The Star Crystal

In the early to mid 1980's there were all sorts of books aimed at pre-teens in which the reader could make various decisions and impact the outcome of the plot. I personally had several different series in this genre (Choose Your Own Adventure, Which Way Books, Find Your Own Fate Adventure). But this is the one book that I still vividly remember. It was different from the other series in that the reader had to solve logic problems to advance rather than just rely on an arbitrary decision. It was so much fun, I read it over and over. I still have a copy, and it is worn out. Looking over it now, it seems a little simplistic compared to the technologies kids play with these days, but it was a lot of fun back in 1984!