I was a huge fan of the original "Rendezvous with Rama". It presented the reader with an incredible scenario and allowed him/her to simply explore it along with the characters- not getting bogged down in cliched details or unrealistically large personalities. At all times it felt like anything could happen, and it was one of the rare instances in which I literally couldn't put the book down.
This book, and the two that follow it, are almost completely opposite of the original in every way. This is a story all about the characters- more so than their mission. I was still interested in returning to the world of Rama and possibly discovering more, and this book didn't disappoint in that regard. However, there were so many cliches and naked plot-devices that it really detracted from my enjoyment. I was especially disdainful of the somewhat hokey "mysticism" with regard to the character of Nicole des-Jardins. That part seemed far more in the realm of fantasy than serious science-fiction.
However, I have read the succeeding books, which I thoroughly enjoyed (though not as much as the original), and "Rama II" is a required read before delving into the third and fourth installments. One must bear in mind that the three sequels are, basically, a separate series from the first book.