The Knockout Fun Book.

The Knockout Fun Book was a companion to the Knockout Comic. It was first published in 1941, was renamed the Knockout Annual in 1957 and ceased publication after the 1962 issue.

Four issues of the Knockout Fun Book contained original stories by Charles Hamilton. The 1955 issue contained four genuine Hamilton stories - you can read it here.

Steve Holland has published an excellent article on the Knockout in his 'After the Magnet' website. You can read it here.

Bill Lofts and Derek Adley published a booklet on Hamilton's work after the Magnet ceased publication in 1940. There is an interesting article on the Knockout on P11-18. You can read the booklet here.