To me, there is really only one name in hiking guides: William L Sullivan. Being that I live and generally hike in Oregon (I usually seem to regret the hikes I’ve taken on the other side of the river), Sullivan’s guides have me pretty much covered. He’s been hiking around Oregon since he was a kid and his knowledge of the trails and parks is second to none.
I mostly use his red book, 100 Hikes in Northwest Oregon & Southwest Washington. My copy is an older edition, but he updates them every year or two to account for changing trail conditions. Inside, the trails are summarized at the beginning in a series of tables (one for each region covered) that rate difficulty and features. Each hike receives a thorough write-up including driving instructions to the trail head and detailed, hand-drawn maps. The newer editions include GPS coordinates for the gadget inclined.
This book has taken me on the best hikes and it is the only book I would bother to recommend for people interested in day hiking. Buy it.