I have most volumes on this huge subject and know two of the authors mentioned above and a couple of the ones listed lower in this post.
It all depends what you want to do, how far you intend to progress and to a lesser extent, what aeroplane you fly.
As much as I enjoy Aerobatics by N Williams it does not tell you how to fly the maneouvers very well, IMHO. Cassidy's book is very prescriptive and it is far easier to cherry-pick than read it cover to cover - a great book if you are intent on improving your aeros.
Flight Unlimited 95 Muller/Carson is a very readable book.
The Szouzy/Goulian books are good as the pictures and drawings are very clear, in fact clearer than Alan Cassidy's.
For neo-aerobatic Pitts pilots, Fly for Fun and Fly for Fun to win by Bill Thomas are very useful material. Spins in the Pitts Special by Gene Beggs is also "character" building!
I've never been brave enough to try aeros in a Cessna Aerobat so really can't comment objectively on Barry's book but it does cover more than just the basics!
The Duane Cole series (Roll Around a Point, Conquest of Lines, etc) are quite useful primers but do not give the the depth or detail that you'll get from Alan Cassidy, Eric Muller or Mike Goulian.
Stik