The book is available at the Baldwin Project, Project Gutenberg, Internet Archive, Hathi Trust, and Google Books. There is also a free audiobook at LibriVox. You can get a free Kindle ebook from Amazon too!
How Arthur Became King
The Good Sword ExcaliburThe Great Feast and What Followed
Arthur's Court and the Order of the Round Table
King Arthur and the Princess Guinevere
The Coming of Gareth
The Story of Sir Gareth and Lynette
Sir Ivaine
Sir Balin
Sir Geraint and Enid
Arthur and Sir Accalon
How Arthur Fought with a Giant
How Arthur Fought with Rome
The Knight with the Badly Made Coat
Sir Lancelot and Sir Brune
The Adventure of King Pellenore
Sir Lancelot and His Friends
How Sir Lancelot Saved the Queen
Sir Lancelot and Elaine
The Search for the Holy Grail
The Death of Arthur