Although Format 2 of the Young People’s Library only was published between 1898 and 1902, all of the titles had more than one cover variant.
Here is a new cover for the database for book #52- The Sleepy King. This Sleepy King is identical to the red covered book already in the database. Even the ads are the same. Both books have ad style “d” (see: http://henryaltemus.com/series/series202F2.htm) which indicates a 1901 publication.

Both books are shown below.