There is no single book that covers both topics in great detail, let alone two books that cover each topic extensively.
David Nicole wrote two books titled Crusader Warfare (Vol. 1 and 2) that are well worth reading, although a bit dry; still recommended. J.F. Verbruggen and John France are also recommended for the European side.
For the Ayyubids the best material is not in books, but in papers written by various scholars. David Ayalon has some very valuable information. H.A.R. Gibbs and Reuven Amitai are well worth digging into. You can find many of their papers on Google Scholar or JSTOR.
I do recommend staying away from gamers material. Much of it is not accurate, especially when it comes to the Ayyubid, Mamluke, and Il-Khanate armies. For example, some describe the qaraghulams as black slave soldiers, which they were not. They were Turks from the Steppe, mainly Qipchaq. One needs to have an understanding of the terms qara (Turkish) and ghulam (Arabic) and how they were used to realize what the two mean. Another, is the term Tawashi (sometimes written as Toassin which comes from a Latin source). Years ago, I was informed by gamers that the tawashi were slave soldiers of a higher pay grade, which I have since learned, after a great deal of research, is inaccurate. The tawashi were free soldiers who made up the core of the Ayyubid army. Question is were they all Arabs or were they a mix of Arabs, Qurds, Farsi and Turks.
Osprey Publishing's newer material is fairly decent when it comes to what the soldiers looked liked. Sadly, there is not a lot of contemporary depictions of what the Ayyubid soldiers looked like. Much has been extrapolated from Mamluke sources of the 13th and 14th centuries.