If you are just starting to learn AppGameKit, then buying both volumes is probably the quickest way to get up to speed with the language (I may be a bit bias). But you can certainly
learn AppGameKit without the books (especially if you already know another programming language) by using these forums and looking at the Help pages available from within
AGK's IDE.
Even after the 1900 odd pages that make up the two volumes, they still don't cover EVER statement in AGK2 BASIC but they do much more than just covermost of the commands of the language; they have extra features such as how to create your own
GUI controls and how to write the AI component of a game as well as the coding of several complete games.
If you go to the Digital Skills website (www.digital-skills.co.uk) you'll find a fuller description of what's in each volume.