I will be reading The Vanishing Trout, based on seeing it listed here and then turning up a handful of reviews on the site here after further research. Picked up a first edition copy off Abebooks the other night.
Other candidates for a re-read this year:
Night Fishing for Trout - Jim Bashline
Taking Larger Trout - Lawrence Koller
Limestone Legends (FlyFishers' Club of Harrisburg, an interesting anthology of articles, stories, and the like)
Currently re-reading:
Fishing Small Streams with a Fly-Rod - Charles Meck
Reading copies of PA Angler, which PFBC has made available online, for all years published. Interesting to see how the ideas have changed over the years; one blurb I recently read talked about a WCO spotting a watersnake out in February; then the WCO killed the watersnake and took it back to his office to prove the snake was out in February.
Report of the Fish Commissioners of the State of Pennsylvania - legislative report prepared from the 1880's through the early 1900's, which contains all kinds of interesting historical fish data and observations (sort of like a precursor to early versions of PA Angler, with a bit more bureaucracy). Has nice color artwork of fish in some editions (attributed to Denton) and I've been collecting them and reading some as I have time.