Herman Hesse I don't believe was a formal Buddhist But:

 I think Siddhartha is written more for a western Mind and sort of by a secular Christian and how he or she would deal with Buddhism. 

However, Siddhartha by Herman Hesse, even though I think it was written in 1922 is still relevant today just like it was relevant in 1966 to 1975 when I bought my first copies of Herman Hesse's works in a college Book shop while I was buying textbooks for my college classes. Siddhartha was the first of Herman Hesse' works I read and later I learned he had been the patient of Carl Jung as well which I found interesting.

Later I read Narcissus and Goldmund, and later still Magister Ludi both of these books for me were very informative regarding college in general for me. Also, around this time I also started to read "Lord of the Rings by J.R.R. Tolkien.

However, at that time I didn't know that Tolkien was a soldier for Great Britain in World War I and that literally all his best friends died in that war. So, writing Lord of the Rings and the rest was Therapy for what Tolkien had experienced in World War I.

Also, he was a Linguistics professor at either Cambridge or another famous English College or university when he returned from the war eventually.