There is a series of books by Evie Litton that are excellent and there are several volumes that different kinds of springs and various areas of the country. His Hiking Hot Springs of the Pacific Northwest (2004) is the best one I have come across and contains very good directions to virtually every spring worth visiting. Jayson Loam's Hot Springs and Hot Pools of the Pacific Northwest is another good resource that includes resorts that feature hot tubs or pools.
ENJOY!!!
Evie Litton is actually quite an amazing woman. I had the pleasure of meeting her at a spring early one morning and felt like a flushing fan when i recognized her and told her what an honor it was to meet her. she's like a rock star of the hot springing community. on that note, her guides are very good but make sure to get the most current edition- as you know, springs change over time and the updates can sometimes prove vital information.
Any current recommendations for Featherville area springs?