There are lots of varying depth and quality. As an ex-student of Barnard and Philpott given the "I strongly recommend you purchase this excellent publication" plug in the first Aerodynamics lecture at Uni, can definitely recommend it. Clear and concise (and without too many formulae for the algebraically daunted). Kermode is also v good. These two should suffice for ATPL studies IMHO.
However if you want to get silly and go for the mindboggling voodoo option, parts of "Aerodynamics for Engineering Students" by Houghton and Carpenter satisfy the niche nicely.
Finally, the Clancy book was excellent and constantly on loan from the library!