Can I choose a different font for the titles?

Yes. Click "Title font" to choose "Same as the puzzle font", one of the fonts in BookyAI, one of 140 Google fonts made for titles (searchable, grouped as Serif, Sans, Fun & kids, Handwriting & script, Vintage & decorative), or a font of your own ("Add my own font": a TTF, OTF, WOFF or WOFF2 file). The title font is used for the book title and the page headings. A Google font is downloaded the first time you choose it, then works offline.