A matt-glossy coating on a book cover can protect your book from wear while also giving it a nicer shine. Coating a book cover in matt-glossy varnish leaves it with a frosted glass appearance.
Place three sheets of newspaper where you will spray the varnish. Spread the sheets so that they cover enough area to catch the varnish when you spray the book cover. Tape two sheets of note paper or a piece of newspaper around the inside pages of the book to protect them from the varnish so that the paper forms a pocket, within which you can hide the book. Place the book open facedown in the middle of the newspaper.
Spray the book cover with clear varnish in slow, even, back and forth motions. Let dry and spray again with clear varnish. Let it dry overnight.
Spray the book with matt varnish in slightly faster, but even motions. Spray the book only once and spray it lightly (don't overlap the spray). Let it dry overnight.
Buff the book cover with a clean, dry cloth. Rub the cover in light circular motions with the cloth. This will bring some of the glossy varnish to the surface, wearing down some of the matt varnish. Rub the book until you get the desired effect.
Acrylic varnish can be purchased at craft and art supply stores. Use acrylic rather than oil-based varnish, since oil-based varnish may take longer to dry and may not be suitable to use on your book cover.