Your favorite guide to Chiang Mai?

I'm an absolute Thailand beginner, just planning a trip to Chiang Mai (and Phuket). I'm basically in the dark about where to stay and what to do, so I'm wondering if you have a favorite reliable guidebook or website to recommend as I begin my research? We're an older couple, looking for cultural sites, mellow walks, slow travel, etc. We're not extravagant but it also won't be a super budget trip.