Psalm 119 is an acrostic Psalm. There are 22 letters of the Hebrew alphabet and there are 22 sections in this Psalm, each one, in alphabetical order, beginning with a letter of the Hebrew alphabet.
This is the longest Psalm and contains some gems. In a devotional style, Vicky Wilkinson does a good job in bringing out the main teaching of each section in the 22 sections of this book.