First off, I enjoyed the book. Good solid information about training in general. For example, the book clearly articulated hard/easy principles, defining what type of training may be classified as "hard" (speed, tempo, long run, etc.), vs. easy (easy 6 - 12 mile runs where you can hold a conversation while running). The book also delves into many details regarding shoes, running gear, etc. Intermixed are runner's stories (which are "boxed off" so you can easily skip over them if you wish to "cut through the chase") derived primarily from these author's encounters of runners who have enrolled in the "Runners World Challenge" in prior years. Many of these are inspiring and helpful, even for an advanced runner, insofar that they remind us that everyone who runs is a winner, and that there are other ways of defining success besides scoring a trophy or PR.
With that said, this book will probably disappoint competitive runners looking for advanced plans that strike a balance between the hard-core running literature for elite athletes and literature written for those with primarily recreational pursuits. In other words, it may be a little conservative for those who recognize that they will probably never score a placing trophy in their age category but nonetheless wish to push themselves to limit of their ability to find out just what they are made of. A particular disappointment in this regard were the training plans, which were few (as noted by a prior reviewer), and generally pretty conservative, save the long run mileage.
In the next edition I would like to see more training plans with more specific guidance on hill training, and making use of the treadmill when hills are lacking (an area in the literature that is lacking, incidentally). I would also like to see more examples...twenty something week plans. Eight week plans (there was one designed to perform consecutive races). Plans with more speed, tempo, and hills (with use of several specific versions of each). In other words, one or two additional levels multiplied by one or two additional longer term and shorter term training plans. Also, more structured guidance on custom designing your own plan and integrating strength training. Add these in, you have a great book on marathon training. To put it another way, the Big Book of Marathon and Half Marathon Training needs to be bigger.