From publisher blurb:
Wondrous Weavings Warped & Weird is an alternate arcane magic system for Old-School Essentials and is compatible with similar clones of the Original, B/X or BECMI editions of the classic fantasy role-playing game.
The system is heavily inspired by how magic works in the stories by Jack Vance and Fritz Leiber. More than a little inspiration comes from fairy tales and folklore too.
These rules apply to both the magic-user and elf class. The referee may of course decide to extend some or all of the following rules to other classes.
The overall result of these rules is that arcane casters are somewhat more versatile and powerful at the beginning, and a bit less almighty at upper levels. The larger impact on the game, however, comes the introduction of Magical Mishaps, which give spell casters the option to increase efficiency and power if they accept a certain degree of risk.