My first game was Avernum 4, and while I liked it a great deal and spent craploads of time last year procrastinating by playing it, I agree it was awfully linear. Good while you were in it, but not much replay value. Avernum 5 is far richer and full of more detail, and there's so many paths you can take that I expect plenty of replay out of this puppy. So buy it? Definitely.