These are a must and excellent read for anyone interested in spirit phenomena/spiritism.
Written by a well known scientist, Allan Kardec, the founder of the science and philosophy of Spiritism. (The study of spirits and afterlife, not to be confused with spiritualism).
I often see posts mentioning that scientists don't take these things seriously and never try to study this field as a proper science. So here is some food for thought for them and for skeptics too, who disapprove the phenomena as crazy BS made up by new-agish nuts.
Easy to read, no mystical hoch-poch here.
The Spirits' Book -
http://www.allankardec.com/Allan_Kardec/Le_livre_des_esprits/lesp_us.pdf (http://www.allankardec.com/Allan_Kardec/Le_livre_des_esprits/lesp_us.pdf)
The Medium's Book -
http://www.geae.inf.br/en/books/codification/mb.pdf (http://www.geae.inf.br/en/books/codification/mb.pdf)