I was already a CLP & CLI (since R3), but bought the book for one of my colleagues who was starting to follow the R4 CLP track in order to become a CLI (Certified Lotus Instructor). I bought it on recommendation from one of my students, having first browsed through his copy.
The colleague concerned passed AD1, SA1 & AD2 all first time. However he narrowly failed SA2, and I would criticise the lack of detail on that area - it had approximately only 60 pages on that exam, compared to over 200 for SA1.
I thought the format was excellent, very readable with good examples, and it covered all the exam topics, especially stressing those such as Shared Mail, which was a new feature to R4 Sys. Admin, but not covered in the equivalent authorised Lotus course since the course changed to cover R4.5 (exam is on R4).
I liked the practice tests in the book, but had just one niggle. The answers were visible along with the questions, so you had to cover them over as you went along. It would have been better if the answers had been in the back of the book.
I thought the tests on the CD were excellent - the closest thing I've come across to the "real thing", both in level of difficulty and the phrasing of the questions. One small niggle again: Unlike the Sylvan Test and other practice tests, you had to check the answer to each question as you answered it, rather than giving you the facility to take the test "blind" and get a score at the end.
Overall, I would strongly recommend the book as an aid to passing the exams, but not as a "teach yourself" book - which it is not intended to be.