What's funny is I was thinking just the opposite - this book benefits from its brevity. Too many sourcebooks seem to be way overpadded with filler material that is there to pump up the page count. This book seems to have been carefully put together, with just the right amount of content. I felt like I wanted more, in a good way. Had it been twice the current size, it may well have been too much of a good thing.
The ideas in this book are intriguing and feel fresh to me. I've never been a huge fan of psionics, but this book has helped nudge me in that direction. I also like, especially, the fact that it directly addresses the "psionics is only for scifi" mindset, and provides ways to make psionics fit comfortably in a fantasy milieu.
Good, solid work.