Light reading
Light reading was any work of literature that was easy to understand and enjoyable to read.
Spock considered works of fantasy, such as Alice Through the Looking Glass, to be light reading. (TAS: "Once Upon a Planet")
In 2366, Captain Jean-Luc Picard took hardcover editions of Ulysses and Ethics, Sophistry and the Alternate Universe with him on his vacation to Risa. Commander William T. Riker disagreed with the captain in this instance as he didn't think of those books as "light reading". (TNG: "Captain's Holiday")
In The Doctor's opinion, the Hansen diaries (the Borg research logs of Magnus and Erin Hansen) were not an example of light reading. (VOY: "Dark Frontier")