A "boomerang book" is a craft where squares of paper are folded into a triangle and then attached together in such a way that they make a book or in this case, an invitation booklet.
Remember: There may be a bit of trial and error in the folding, so practice with white paper to get your folding technique down and then go to town crafting this spectacular spider invitation.
Supplies
5-inch square of white paper with "You're Invited" spider web design
5-inch square white paper with party info spider web design
3 sheets black cardstock (8 1/2 x 11 inches)
1 sheet fabulous yellow paper with glitter swirl design
Double-stick tape
Scissors
White glue
2 yellow diamond-shaped acrylic gemstones
Directions
To Fold Triangle:
Practice folding 5-inch squares of plain white paper first to master your technique. Refer to the photo below of the open invitation that has the spider web design and spells out "You're Invited."

Fold the 5-inch paper square in half on the diagonal, corner to corner, and then fold it in half on the opposite diagonal. (The square should have 2 creased lines that form an "X" and 4 triangle quadrants.)
Fold the paper in half to make a third crease that will bisect 2 of the triangle quadrants.
Bring the 2 bisecting creases together touching and lining them up middle of the square and then push down on the outer triangles that don't have the creases.
For Invitation Booklet:
You should now have a folded triangle that opens up into a square resembling the "You're Invited" paper in the photo above. However, you'll notice the "You're Invited" paper is an octagon. Snip off the corners of the folded triangle to turn it into an octagon.
The 5-inch squares of white paper with the "You're Invited" spider web design and party info were made in a computer drawing program, but you can also make the squares with the printed title and party info and have the kids decorate them with markers. Whatever works for you!
Fold the 5-inch squares into triangles. Place the first "You're Invited" triangle or page of your invite directly on top of the second party info triangle and use double-stick tape to attach them together on the bottom of the first triangle and top of the second triangle.
Open up the triangles and you should have a 2-page invitation booklet. (You can make as many pages as you like. I thought 2 were plenty for an invite but the more the merrier!)
For Spider Body:
Cut 2 oval spider bodies out of black cardstock large enough to completely cover the closed booklet. The ovals should be about 6 inches long and will be the front and the back "covers" of the book. Use double-stick tape to attach the black ovals to the first and last page of the closed booklet.
Cut 2 round shapes for the spider's head one slightly larger than the other. Place the smaller shape on the lager shape and attach them with double-stick tape and then attach the head to the body.
Use white glue on the back of the yellow diamond-shaped gemstones to attach them to the head as the spider's eyes.
Cut 8 spider legs and curl the ends a bit to give them a creepy touch and use double-stick table to attach them to his body.
Cut the fabulous yellow paper into a pointed oval as a final accent on the spider's body and use double-stick tape to attach it.
That's it! Send your spooky spider to guests inviting them to your Halloween shindig!