We have published two books through Leanpub. They are not yet 100% complete but they are available for download.
R for Photobiology: Theory and recipes for common calculations
https://leanpub.com/r4photobiology
This handbook describes how to use R as a tool for doing calculations related to research in photobiology. Photobiology is the branch of science that studies the interactions of living organisms with visible and ultraviolet radiation. The most frequently used calculations are related to the characterization of radiation and of the responses of organisms to radiation. Many of these calculations are also used in Biophysics, Meteorology and Geophysics.
Learn R …as you learnt your mother tongue
Learn the R language as a child would: Do not struggle, just play! If going gets difficult and frustrating, take a break! If you get a new insight, take abreak to enjoy the victory!