Neal Asher's "Cowl."

I finished reading it a few months ago and my mental muscles are still aching a bit from the workout this book's mutiple shifting of time streams. This books not only demands the readers' full attention, but the ability to read the convoluted temporal map the author unrolls as the novel progresses. This is not an easy read, nor a terribly satisfying one if you want a stopping point to take a breather...but it is a worthwhile exercise if only to see what an exceptional author can do in trumping other stories where time travel is a central (but far from only) theme.

Mr. Asher's novel "Skinner" (also in the SF genre) is brilliant as well. Read it. You may not go swimming or on a vacation cruise afterward, but it will have been worth it. For biologists and parasitologists with a little time on their hands, read this book and then thank your lucky stars for our planet's fauna.

Thanks for the recs!  DH reads SciFi and can't find much with any substance.  He's really picky.

I love "time travel" genres... I'monna look this one up! Thanks!

i am reading Gene Wolfe who is not an easy read either but well worth the time it takes to read; very good author!

Stealing the Elf-King's Roses by Diane Duane. Definitely has some fascinating science with a little bit of magic mixed in.