There are quite a few around and the best will depend on which type of aircraft you are going to use.
With my tongue firmly embedded in my cheek I can recommend "Basic Aerobatics" by Ron Campbell and Barry Tempest if you are usung a Cessna Aerobat as it really was written round that aeroplane type and its characteristics. Some facets of legislation are a little dated as it needs a new revised edition in that respect. Possibly early in 2005. Hope you really enjoy aerobatics: it has been my chosen sport and pastime for over 50 years.
All best wishes,
Trapper 69
(Barry Tempest MRAeS)
Armageddon Aerobatics
www.tempest.ndo.co.uk