He mentions this surprising fact in an interview with the Dallas Morning News, which has been picked up by Politico.
In addition to being surprised that he can read, Mr Bush says, many people are surprised that he has some talent as a painter, which he describes with a little self-deprecating humor. He makes it sound like a kind of sissy-sounding hobby that he took up in retirement only because Winston Churchill said it was okay. (That said, we really do like his paintings of his dog).
In other news, recent polls suggest that his administration is still better-loved than Nixon's. However, its popularity appears to be dropping retroactively. James Buchanan had better look to his laurels.