From Wiki:
Obi-Wan's life between
Revenge of the Sith and the original film is portrayed mostly in
Jude Watson's
The Last of the Jedi series. Set roughly a year after the fall of the Republic, the series follows Obi-Wan as he seeks out possible survivors of the
Great Jedi Purge, most notably Anakin's former rival Ferus Olin. The books also portray Obi-Wan adjusting to life as a
hermit on Tatooine, and quietly watching over Luke. He also discovers that Vader is still alive after seeing him on the Holonet, the galaxy's official news source.
Obi-Wan appears in the final chapter of
Dark Lord: The Rise of Darth Vader, set just after the events in
Revenge of the Sith. He is also the protagonist in
John Jackson Miller's novel
Star Wars: Kenobi, which takes place during his exile on Tatooine.