My list of authors whos books I automatically buy as soon as there is a new release ist:
Jim Butcher (the dresden Files and Codex Alera series)
Anne Bishop
Diana Gabaldon
Patricia Briggs
Christine Feehan
Sherrilyn Kenyon (dark, were, dream hunter books)
Tamora Pierce
Clive Cussler (dirk pitt books)
J.D. Robb
Karen Marie Moning
Yasmin Galenorn
Katie MacAlister (her dragon books)'
Jacqueline Carey
Joey W Hill
Traci Harding (although I have some difficulties getting her books as they are first only published in Australia
)