Ko vs AoII
Before I startd learning a count, I bought both books and tested both books in sims. Asked everyone alot of questions, and found some people playing both in casinos.
I discovered that AOII detects changes in the deck much faster, is more true to what is actually going on in the deck. Its better for insurance, and strategy (as to when to deviate from basic strategy)
All that being said I chose KO.
Why?
Ko is about 100% easier to learn and to use.
I found out that for a person starting out in a casino, its hard to count and adjust bets and estimate true count ect.
I may switch to a smaller version of AOII where I use the tags from the system and add insurance and the Illustrious 18 by Don S.
That should yield more than KO prefferred.
Ko will make money, so I would run buy the book if I was you...