Source: HalfLife2.net

Prima Games has put online two Look Inside features for their upcoming Half-Life 2 books, namely the Half-Life 2: Official Game Guide and Half-Life 2: Raising the Bar. Do note that the previews of both the books can contain Spoilers for some, so if you would like to play the game as spoiler free as possible then don't view the content linked below:

Both the files are in .pdf format which means you will need to have Adobe Acrobat (Reader) installed.

'Look Inside' Half-Life 2: Official Game Guide
'Look Inside' Half-Life 2: Raising the Bar

As soon as both the books are in I'll put online a small review of them.