For some reason, I read Shakespeare comedies while writing Robin Hood tales, and draw (pun intended) on the original Robin Hood folk ballads as preserved in the 16th and 17th century plays and broadsides, as well as the Victorian era adventure books.
Often reprinted and still the best:
Robin Hood and the Men of the Greenwood by Henry Gilbert (1912), illus. by Frank Godwin
Robin Hood and His Merry Men by E. Charles Vivian (1906), illus. by Harry G. Theaker and Jules Gotlieb
The Merry Adventures of Robin Hood of Great Renown in Nottinghamshire, written and illustrated by Howard Pyle (1883)
Maid Marian by Thomas Love Peacock (1822)
Ivanhoe by Sir Walter Scott (1819), illus. by N. C. Wyeth