The 'For Dummies' books have an unearned stigma, I think. In general, books that survey subjects are considered inherently flawed because those that are "in-the-know" feel slighted by the lack of nuance these books give to their subjects. My feeling is, they're not meant to, and I've always thought the 'For Dummies' books were great for everything I've ever turned to them for. They do a great job of covering the entirety of a subject enough to hammer home the fundamentals but provide enough suggestions for further study for those interested.
While I don't have a great basis for comparison, I thought this book was surprisingly informative and I highly recommend it. If anything, the casual reader may find it too informative than their modest need of it requires. It contains and explains (sometimes ad nauseam) everything from the essential dogmas to church hierarchy and history to the saints to the presence in the Eucharist, etc.
I actually read this one cover to cover like a regular book, but most people will probably buy this book for reference. I actually wouldn't recommend it for that. Use the 'Catechism of the Catholic Church' instead. Although, these two books together were a great way for me to introduce myself to Catholicism.
It's only fault I thought was all of it's think-of-it-like-this analogies when describing doctrinal ideas seemed panderous and read more like apologetics than explanations. But, to be fair, the book was also surprisingly honest about dissent of some church members about current practices in the Church since the reforms of Vatican II, and the current molestation scandals in the clergy. It's concise history of the church in Appendix A is biased, but it admits as much, which is admirable.