There are many sound doctrinal book written over many centuries. Below are books are I recommend and feel are well worth the time to be read. However, first start with the Holy Bible. Read the precious word of God from cover to cover, study it daily and never neglect it.
Books on Sabbath Observance
The Ten Commandments by Thomas Watson
Call the Sabbath a Delight by Walter Chantry
The Day of Worship by Ryan M. McGraw
The Pilgrams Progress by John Bunyan An Allegory
Prayer by John Buynyan
Life in Jesus Edited by Octavious Winslow A memoir of Mary Winslow.
The Christian’s Great Interest by William Guthrie
*Please note: I am in no way affiliated with the above authors or the books publishers.