Sans forgetica

Sans forgetica is a variation of a sans-serif typeface, claimed to assist students in retaining the information which they read. Two years after its release and having received a great deal of publicity, the first peer-reviewed study demonstrated that Sans Forgetica was not effective for enhancing memory. Back-slanted and with gaps in the letter forms, the typeface is designed to reduce legibility; it adds reading complexity to learning tasks based on the psychological principle known as desirable difficulty. It is licensed under the Creative Commons Attribution-NonCommercial license.

From the Wikipedia article “Sans forgetica”, licensed under CC BY-SA 4.0.

Sans-serif faces work well for headings, captions, children's books and modern nonfiction. For long-form body text in print, most designers still prefer a serif.

Commercial typefaces require a licence that covers embedding in PDFs and ebooks; check the foundry's licence before you publish.