Everybody who includes a cover image has text in their images. Like mzmm said, as long as it is incidental text, and as long as you have reasonable alt attributes so that someone using a screen reader doesn't get too confused, you should be fine.
Wait, this is a fixed-layout book? Why aren't you including the text as... you know, text. It should be in an SVG text tag so that it is searchable. I'm assuming you created the text in an app like Photoshop or Indesign, right? If so, you should be able to export in a way that preserves the text as text.