Welcome to the forum "loo".

There are a whole lot of great PS books out there, and there are some "not-so-great" ones too. I guess to give you the best answer, i'd have to ask, "What do you want to do in Photoshop?" The answer can help us direct you to the best books for that purpose.

Some of the members here use PS for photomontage and photo-manipulation, for that i'd recommend:
Adobe Photoshop Master Class
or
Photoshop 7 Artistry: Mastering the Digital Image

Still other members are looking more towards design, web graphics... for that i'd recommend:
Adobe Photoshop 7.0 Studio Techniques by Ben Willmore, (one of my favorite "PS guru" authors)
another would be
Photoshop WOW (as stated above) by Jack Davis (another favorite "PS guru" author)

I can give you the "names" of some PS authors that have consistently put out extremely useful books and they are:

Ben Willmore
Jack Davis and Linnea Dayton
Scott Kelby
Deke McClelland

these guys maintain a large area of my bookshelf...

see ya' around.
:)
retrocity

ps. did you want to discuss your "horse" concept??