My favourite standalone book: 'Goodnight Mister Tom' by Michelle Magorian
My favourite short series: 'Ice Station', 'Area 7' and 'Scarecrow' by Matthew Reilly
My favourite long series: 'X-Wing' (various novels) by Michael A. Stackpole & Aaron Allston
My favourite epic series: A tie, between 'The Lord of the Rings' by Mr. Tolkien, and Stephen Lawheads 'The Pendragon Cycle'
I also like the hitchikers guide, but I agree with bart on the fantastic but possibly only up to the end of the second. I've never managed to finish 'so long...' and I've only ever read a few lines of 'mostly harmless'. But still, a trilogy in five parts, genius

Yoda, reading lots