I bounced hard off of Tinker. Got about halfway through before I decided that nothing was going to make me like the book one iota better and put it down.

A lot of it had to do with magic-as-engineering - I prefer a sense of the numinous instead, and pinning it down with rules explicitly stated in the text kills it dead for me, like a bug mounted on a pin - yeah, you can see it all and it's there, but there's something vital missing. I don't mind engineering-type novels, actually, I rather like books about engeneers and tinkerers and mech-heads building and experimenting and achieving; it's just I don't like the intersection of the two.

The rest of it was the characters - Tinker started out as interesting, but I didn't really like anyone else, and once I realized I no longer cared what happened to Tinker, it was time to stop reading. :)