The PMBOK Guide is a standard for the project management profession. Its intention is to serve as a guide to the body of knowledge within the project management community and as practiced by members of the profession. There is no single document that contains the project management body of knowledge. Indeed, some of it is not published at all but, rather, is simply recognized as good practices and norms within the profession. This body of knowledge is growing every day.
The PMBOK Guide is not intended to be used to learn project management or project management concepts. It's especially not intended to teach or suggest PM techniques or methodologies.
It's not a "how to" book nor is it a description of a methodology. It's a standard, not a methodology. PM professionals and the organizations they work for can use the PMBOK Guide as a guide for developing their own methodologies or for creating organization standards.
It's particularly important to understand that it is not a standard or specification for the examination portion of the PMP certification. For one thing, at least 30% of the material on the examination is not covered by the PMBOK Guide. (There IS an exam on the PMBOK Guide. It's the CAPM exam, which only covers knowledge of the PMBOK Guide.)
While the PMBOK Guide only changes once every 4 years, the exam component of the PMP credential is constantly changing. Much of the material that showed up in the 4th (2008) edition of the PMBOK Guide has ALREADY been showing up on the PMP exam for several years - e.g., PTA, TCPI, etc. PMBOK Guide 4th edition came out in December, 2008, but these topics have been showing up on the PMP exam as early as 2006. The group at PMI that develops the standards (such the PMBOK Guide, the Standard for Risk Management, etc.) and the group at PMI that develops the the certifications and their corresponding exams (such as PMP, CAPM, PMI-SP, etc.) are two separate groups that DO NOT interface with each other. They are two separate groups. If anything, the standards group looks at the work that the credential group (PMP, CAPM) does and uses it as one of the many inputs for what they put into the standards such as the PMBOK Guide.
A reviewer here, on Amazon, observed that there is a widely held notion that PMBOK = Project Management. I disagree with that observation. The false notion he observed is only held by those people who do not know what the PMBOK is. Also "PMBOK" is not the same as "PMBOK Guide." PMBOK is an acronym for the Project Management Body of Knowledge. As I said, above, there is no single document that contains the project management body of knowledge. It's simply the body of knowledge that is collectively known among practitioners. academics and organizations who practice or research project management. The document known as the PMBOK Guide is simply a guide to that massive body of knowledge; an entry-point to further information and a standard for developing protocols, methodologies, techniques and practices within your own organizations and project management practices.
The PMBOK Guide is a reference work, not a text book or a study guide. It's not meant as an introduction to project management any more than a volume of statutes is meant to be used as an introduction to the practice of law or the Physician's Desk Reference (PDR) is mean to be used as an introduction to pharmacology for doctors and pharmacists. As with technical references for other professions (such as statute books for lawyers, clinical references for doctors, etc.), non professionals may find the PMBOK Guide difficult to follow and even dry. An experienced and trained project manager should find the PMBOK Guide perfectly understandable and not very difficult to follow. An experienced and professional project manager looking at the PMBOK Guide for the first time may find its format unfamiliar (at first), but he/she should find the material and the concepts in the document familiar (though organized in a way they may not be used to).
On the other hand, an entry-level project manager, or a non-project manager who is thrown into project management tasks may, indeed, find the PMBOK Guide difficult to follow and difficult to understand. This is not unlike a sophomore accounting student opening up a set of GAAP or IFRS guidelines and finding it hard to follow or finding the writing style very didactic and anything but light reading, while this would NOT be the experience of a certified CPA or an experienced accountant or financial professional.
Very important: The PMBOK Guide is not an I.T. text nor should it be considered part of the literature covering the topic of information technology. For some reason, the document is shelved in book stores along with I.T. books. It really should be shelved with books on management. In the same way, PMP examination study guides are also shelved next to I.T. books. The PMP credential is not an I.T. "cert." In fact, it's not even in the same class or category of "certifications" as technical and I.T. "certs." The PMP is a professional credential, in the same category of certifications for other professions, such as accounting, law or medicine. Unlike I.T. "certs", where the only requirement to earn the certification is the ability to make an appointment at the Prometric center and where the only criteria for earning the certification is the ability to pass a test, the PMP credential has experience, education, continuing education & professional contribution requirements. There is also a requirement to adhere to a professional code of conduct.
Because of the "cert" fever within the I.T. community and among I.T. workers, many non-PMs in the I.T. sector are pressured to add the "PMP" letters to their names. Recruiters are among those who create this pressure. Because they are not experienced project managers, these I.T. people are pressured into lying about their background and skills during the PMP qualification process -- and getting friends to lie during the audit and vetting process. This may account for the number of (dishonestly earned) PMPs out there who may have the letters after their name (though they got those letters under false pretenses) but who are not really project managers at all. This is why people see a lot of "PMPs" who have no idea about what they are doing.
Project management is a profession. While there are many professional project managers out there practicing their profession, there are quite a lot of non-project managers who have been thrown into PM responsibilities and roles. While they do, indeed, hold a "job" as a "project manager" and are being asked to perform the tasks of a project manager (and may even have a title called "project manager:), they are not project managers. They're just people who have been asked to do the work of project managers.
The PMP credential is not for people want to move into project management. It's for people who ALREADY ARE project managers and have been for several years. The PMP credential verifies that the individual has the education, years of experience, professional training, adherence to a professional code of ethics, commitment to ongoing continuing education and commitment to ongoing contributions to the project management profession. The exam portion of the credential verifies that, in addition to all of the above, the individual has an understanding of the profession he/she has been practices; that the individual knows that project management is NOT common sense and that he/she is not managing project by seat of his/her pants or via intuition; that the individual understands that sound project management is based on the past experiences of other members of the profession, based on research and sound empirical (scientific) study; that the "art" and practice of project management is based on science, not intuition.
Finally, as to the question "what would be the best alternative book": there is no alternative. The PMBOK Guide is the accepted global standard and the recognized guide to the project management body of knowledge. That's all it's intended to be and it serves that purpose well. It's not the end to all ends. The members of the project management profession who contributed to the document did not aspire to cover all there is to know about project management. It's not perfect and it's constantly changing (every 4 years) as the profession continues to grow and mature.
You can (and should) supplement the PMBOK Guide with other PMI standards and frameworks -- e.g., The Standard for Program Management, The Project Manager Comptency Development Framework, The Practice Standard for Work Breakdown Structures, etc. There are supplemental standards and frameworks developed by other professional and academic organizations as well. However, as the GUIDE to the "body of knowledge" within the profession, the PMBOK Guide is the standard. There are other books and sources on other topics of project management, including sources on methodologies, leadership, PM tools, general management, the management of people, budgeting, scheduling, quality management practices, organizational behavior, etc. as well as industry specific literature on project management, such as marketing project management, I.T. project management, construction project management, research & development project management, etc. However, such topics are outside the scope and purpose of the PMBOK Guide. Of course, since anywhere from 60% - 70% of the material in the examination portion of the PMP certification either comes directly from the PMBOK Guide or requires understanding of the concepts in the PMP Guide, a knowledge of the material in the document is important to anyone who is planning to sit for the exam. So, while the PMBOK Guide is NOT a study guide for the exam and is not intended to serve as such, familiarity with it is important part of both practicing the PM profession as well as earning the profession's certification.