I made this golden grimoire
I took a large pre-made book shaped box from my local crafts supply shop and covered the spine, back and the margins of the front cover in leather.
Spine
The leather on the spine has rougher texture than on the rest of the box/book and I first covered it in copper coloured gilder's polish, while allowing some if the reddish brown on the raised areas on the leather to show through slightly, after which I sealed it with two coats of clear exterior polyurethane varnish. You can see how beautifully it sparkle under lights in the final picture in the series attached to this post.
Back Cover
On the back I unfortunately had to use multiple pieces of smooth black leather to completely cover it since I didn't have a single piece large enough. I attached the leather with a standard contact adhesive.
I applied 5 or 6 thinish and even coats of a pale gold coloured acrylic paint to make sure the black colour of the leather was properly covered (a hairdryer certainly is a timesaver here) and once again sealed it with 2 coats of clear varnish. To protect the finish from scuffing and other damage while the box/book is laying flat, I hammered in a bunch of nickel plated upholsterer's tacks along the back's edges.
Front Cover
For the front cover panel, I cut strips of slightly textured leather that would cover the +-6mm thickness of the outer edges of the piece as well as a 3cm band along the edges of the front. This left a big open space in the middle for the mosaic. Then it was painted and sealed the same was as the back of the box/book was.
On the inside of the front cover, I cut 3cm wide strips of thick cardboard and painted them the same colour as the outside. I glued them around the edges of the inside cover, leaving a space that I filled with a rectangle of thicker cardboard I painted a dark (almost imperial) purple. Once again 2 coats of clear varnish was applied.
Inside
On the inside I went for contrast and covered almost the whole inside with sparkly silver tiles with some small sparkly gold tiles along the inner edges. As a centrepiece for the interior, I created a mini stained glass window from several different coloured small sparkly tiles.
Mosaic
Finally the main event. I decided I wanted a mosaic on the cover of the box/book that looked like a stained glass window from a church/cathedral. I didn't have anything sketched out, I simply went with what came into my imagination.
I used small white tiles to make the "frame" and filled in the various panels with whatever combinations of the colours I had available in my big box of mosaic tiles that looked good to me. The little round "rose window" was filled in with small sparkly tiles so it stands out under bright lights. Finally I filed in the gaps between the tile pieces with black grout that looks almost like the lead in a real stained glass window.