(Wells added this epilogue to the American edition, and it wasn't in the original magazine version.)
In the epilogue, we meet a man who owns an inn/bar in Port Stowe called "The Invisible Man." Turns out the bar owner is Marvel.
After the Invisible Man was killed, they couldn't prove whose money Marvel had, so Marvel got to keep it. He also got some money for doing a one-man show to tell about his experience with the Invisible Man.
Apparently, Kemp has been looking for Griffin's books, but Marvel tells people that he doesn't have them.
Lies! In fact, Marvel does have the books, and he looks at them sometime, though he can't figure out what Griffin wrote.
Marvel thinks sometimes about what he would do if he were invisible...
The book ends with the idea that those scientific notes hold "the subtle secret of invisibility and a dozen other strange secrets" (Epilogue.11). Sequel, anyone?