[Pentegarn]

There's a few good "x best board games of all time" books worth looking into. But to get really into how to design a great game you have to learn what works by playing them. Watching the trends is a good thing too. Like right now the co-op games and deckbuilders are scoring huge. Going to both Gen-Con and Origins is a must as well. You can talk to a lot of game developers there and see the nuts and bolts of how it all comes together if you find the right peeps to talk to. Demo anything and everything, not just to see what works, but to see what does not so you don't repeat the mistakes of a poor game design with a pretty finish,