I had thought someone else would pipe up with this by now --- and not to be judgmental about different options here (!), but how about just continuing to hike? Rain won't make you melt. Perhaps my attitude is based on living in the rainy PNW, but just find a sustainable pace that keeps you warm enough, tune gear appropriately, and truck on. If you must break for any length of time during the day (extended lunch perhaps), put up a tarp or your tent to do so. Et voila.

The times that I find time on my hands is in late fall, winter, early spring trips where there just isn't that much daylight. Apart from relatively clear sky and fullish moon nights, I'm not inclined to night hike as a regular thing, so indeed having some eBooks on my smartphone is helpful.