OK, so calling it a "pattern" might be a bit much. The knitting itself is crazy-easy, but there is one little step at the end that really makes it neat. (And sort of worm-like, if you picture a worm squeezing in and out to move along the earth.)
Here's what you do:
Using about size 4 needles and worsted weight yarn, cast on 9 stitches. Slip the first stitch (knit-wise), and work in seed stitch starting with a purl. (So, sl 1, p, k, p, k, p, k, p, k.) The next row, and every row thereafter, keep slipping the first stitch and continue working in seed stitch. Go until the bookmark is about 6 inches long, and then cast-off.
But don't weave in the ends yet!
Instead, wet the bookmark thoroughly in cold water. Pin the top edge to a sturdy blocking surface, and pull the other end down to make the bookmark about 8 inches long. Pin the other end, and leave the bookmark alone for several hours, until it dries.
See what that little stretch does? It makes the sort of lumpy seed-stitch look even and elegant, and it gives the bookmark just a teensy bit of a flared shape at the ends. Lovely!
Once it's all dry, remove the pins, and weave in the ends. If you need a book to enjoy it with, may I recommend Notes from a Blue Bike? I spent last week listening to the audio book and very much enjoyed it!