Additional texts for preparing the exam

Has anyone used/is using Havels Learning System’s books for exam preparation? has anyone ever heard about them? There is also available from the same publisher a “question bank” with a lot of practice problems but I’m not sure it can be useful.
In general, which are your favourite additional texts (in addition to the curriculum) for preparing the exam and in particular which of them are more easily understandable and time-saving?
Many thanks in advance.

i tried the Havel’s FRM book part 1
the book itself is very well organized by topic/section and has a lot of exercises exam-style, so it is ideal for reviewing the material. having said that, the problems are not particularly challenging (though i only tried a few exercises relevant to me). if you are just starting out, the Havel’s book can help you spot your weakest point that you need to work on. if you want something to see if you truly mastered the material, you might want to look elsewhere.

(this is for FRM, but i expect their CFA book to be somewhat similar in how the problems are organized and the difficulty of the problems)

You are confirming my first impression. Books that summarize the CFA curriculum are very easy to understand and topics are explained in a simple and short way focusing on fomulae that are most useful in the exam. The main disadvantage is represented by the practice problems at the end of each reading that are too easy in comparison with those in the cfa curriculum.

Using the actual CFAI readings is a relatively new thing.
In the olden days, the exam fees were lower and didn’t include the readings, and many candidates only bought notes from a prep provider. Historically, I believe that Schweser was the market leader. The study notes were both quicker and cheaper than buying the actual readings.
Then CFAI changed the rules and bundled the readings in with the exam fees.