It composes of a getting started chapter plus a walkthrough with text and videos of all 11 stages in the game.
It also provides an 'Extras' section for each mission, which gives you ideas on alternative ways to play each level, as well as providing vehicle and special weapon locations if they can alter your way of playing.
While playing press [Al[Tab] to switch to Desktop and then go into the "Userdein_nahmesave" subdir of the game install dir. In one of the subdirs you'll find save.fps file. Delete it, press [Al[Tab] to switch to game and you'll be able to use the save function again!