This blog post is basically a handy list of written resources for those interested in Just intonation and microtonality starting from the simplest to the more specialized and detailed. We suggest owning hard copies as all serve as important references.
The Just intonation Primer by David B. Doty
http://www.dbdoty.com/Words/Primer1.html
Just Intonation Explained By Kyle Gann
http://www.kylegann.com/tuning.html
On The Sensations of Tone. Hermann Helmholtz
http://store.doverpublications.com/0486607534.html
Genesis of a Music by Harry Partch
https://monoskop.org/images/b/be/Partch_Harry_Genesis_of_a_Music_2nd_ed.pdf
Divisions of the Tetrachord by John Chalmers
http://eamusic.dartmouth.edu/~larry/published_articles/divisions_of_the_tetrachord/
Microtonality and the Tuning Systems of Erv Wilson by Terumi Narushima (available in Octotober 2017)
https://www.routledge.com/Microtonality-and-the-Tuning-Systems-of-Erv-Wilson/Narushima/p/book/9781138857568
Musical Mathematics by Cris Forster
https://www.amazon.com/Musical-Mathematics-Science-Acoustic-Instruments/dp/0811874079
Harmonic Experience by W. A. Mathieu
https://www.amazon.com/Harmonic-Experience-Harmony-Natural-Expression/dp/0892815604
'Temperament' and 'Temperament; or the Divisions of the Octave' R.H.M. Bosanquet
http://anaphoria.com/library.html
Greek Musical Writings: Volume II, Harmonic and Acoustic Theory. Edited by Andrew Barker.
https://www.amazon.co.uk/Greek-Musical-Writings-Cambridge-Literature/dp/0521616972
Multiple Division of the Octave and the Tonal Resources of 19-Tone Temperament. Mayer Joel Mandelbaum. Thesis
http://anaphoria.com/mandelbaumthesis.pdf
The Greek Aulos by Kathleen Schlesinger
https://archive.org/details/KathleenSchlesingerTheGreekAulos
Augusto Novaro Musica Natural and approximation (Two editions) 1927-29 and 1951
http://anaphoria.com/novaro.html
Tuning and Temperament: a Historical Survey. Barbour, J.Murray 1951
https://archive.org/details/tuningtemperamen00barb
This list also covers much of a Just Intonation nature that best is seen there as opposed to copying.
http://sacredrealism.org/catlamb/tuninginformation/resources.html
I will be updating this as i am sure i am forgetting many