Final Making Book Update
I went over making and using a basic jig in Part I, and went over a few refinements in Part II. I'll try to wrap everything up here so maybe if you want to attempt this for yourself sometime you can dispense with the steep learning curve I had to endure.
I'll clearly mark some of my lessons-learned.
Don't try to skimp on the paper by using "booklet printing" on a single print. Go ahead and combine two copies of your PDF into one larger PDF and then print that larger PDF to booklet printing.
When your paper comes out of the printer it is essentially "pressed" by the printer with a slight curve. Some printers do this more than others, but they pretty much all do this. It might not even be noticeable, but over the course of a stack of pages it will be noticed. With a single-copy booklet printing the last half of your pages will curl away from the front half of your pages and you'll get a noticeable split right down the center of the book. By combining the same PDF twice and booklet printing you'll still have this curl, but when you cut the pages each book will have all its pages curl the same way.
The picture on the right is not a good example of this curl because I did do the combined PDF print. In this case I screwed up because I made a change to the print job (I actually printed four copies at once and didn't account for this) that I had to correct by printing the "back half" separately. At least I was able to combine similar curls. The 1st two books (left to right) came out good, the third shows the curl and the fourth...well you can see the midpoint of the book because the rate of curl was slightly different. Believe me it is much more pronounced on a single-copy booklet print.
If you are printing a cardstock cover, make sure you account for the width of the spine! This is the biggest reason I hadn't printed anything at 100%. I do have some legal cardstock so I can print up to about 75% as long as the book isn't too thick. You could get the cover printed at Fed-Ed Kinkos though. I'm pretty sure they have 11" x 14" cardstock and a print would be about $2.....well that is the cost for a 11" x 14" self-serve paper print in color at my local stores....
When gluing the pages, use thinner layers of glue and make sure the glue is nice and level. I found that using a q-tip to dole out the glue on the spine when the book is either in a jig or secured by binder clips works well. I like to go over it with one of my wife's cosmetic sponges. The glue will self-level a bit, but careful application goes a long way and pays dividends when it comes time to add the cover.
The final, and arguably most important piece of advice, especially if you have access to a heavy-duty paper cutter is to allow some space to trim up the book once everything is done. All you need to do is square-away the spine and then trim up the other three sides. This, more than just about anything else, allows you to make the finished book look nice. Assembling the book with a good 1/4" extra on the three sides really helps a lot. If you are printing a 50% size book the easiest way to give yourself some "wiggle room" is to select "binding right" as your print option when doing the booklet print. This basically puts the spine of the book towards the inside so when you cut the pages in half you have space on all four sides of the page. With "binding left" the spine of pages is on the outside and when you cut it down you might not have a lot of room to work with when the pages glue up. If you take it in for spiral binding, you might lose some content to the binding as well.
Creature Compendium at 75% (I think) of the regular size. I was fully intending to make a half-page Dyson's Delves II book...well actually two of them, when I tested doing a booklet print of a booklet print and found that page size was pretty cool. Of course, stupid me, I didn't do the mental math and start with a 4x PDF copy so I'd get four sets of printing with homogeneous curls. My printing gave me four sets of 1/2 books (2 front halves and 2 back halves) I probably should have just tossed the paper and started over, but I tried to salvage things by reverse-printing the PDF I had and then matching up front & back halves with the appropriate curls. Not quite right, but close.
All-in-all I'm pleased and think I could make more books as I need/want to. Of course I don't need any more copies of Dyson's Delves II and I'll be reaching out to Dyson to see if he has any state-side people he'd like me to give these to. Please don't ask me for a copy because I'd rather just trash these than undercut Dyson.