The masculine noun sefer (the accent is on the first syllable, since it is a segolate noun) means "book, writing, letter, document, or scroll" in Hebrew:
"This book of the law (sefer hatorah hazzeh) shall not depart out of thy mouth; but thou shalt meditate therein day and night, that thou mayest observe to do according to all that is written therein: for then thou shalt make thy way prosperous, and then thou shalt have good success."