For Fitzpatrick, are you referring to the orange/skin-coloured book, or the "new senior mathematics" one?
This is my opinion on the difficulty of textbooks in descending order:
1. Terry Lee
2. Cambridge
3. NSM
4. Coroneos 4U + supplement
5. Patel
6. Fitzpatrick
Terry lee is a solid pick. Cambridge has diagnostic topic tests at the end of each chapter which can be good for revision but some of the worked solutions for the examples can be difficult to understand. Patel and Fitzpatrick are very easy textbooks.
Although Patel and Fitzpatrick may be seen as good for grasping an understanding due to having easier examples, in actuality, oftentimes the textbooks are flooded with repetitive examples which places emphasis on rote learning rather than understanding.
Coroneos has a pretty good reputation and is generally favoured by math teachers. Personally, I can't stand the terrible font and some of the explanations are hard to follow.
Depends on the topic: Coroneos is the best one for complex numbers. Cambridge is only good for practice/harder Q not really for learning new concepts. Patel is good for integration except for maybe the examples, and is a good revision resource (same guy wrote the Ext 2 Excel textbook)
Fitzpatrick/NSM* is bad for complex numbers, avoid it for that topic, for the other topics and some of the questions are either really easy, or difficult; recommend it for banked tracks, conical pendulum and maybe conics. The old Arnold and Arnold has killer reduction questions. *same author if I remember correctly.
NSM in my opinion is actually easier than Fitzpatrick as it adds pesky multiple choice questions and is "more balanced" than the older Fitzpatrick; wouldn't recommend anything in that textbook, except maybe some questions, some times the NSM dilutes the older Fitzpatrick.
(NSM is the newer version of Fitzpatrick). The problem with both is that occasionally the author makes errors.
