Shaarei Kedusha By Rabbi Chaim Vital (1543-1620), the foremost disciple of The Ari.
An inspirational work containing instruction and exhortations for a life of outmost holiness, which will ultimately elevate the person to the point where he will be worthy of Divine inspiration (ruach hakodesh). (vowelized text / menukad)
The book also includes:
Sod HaNachash by Rabbi Yosef Gikatilla