In the Print Booklet dialog box click on the "Print Settings" and then tick the "Print Blank Pages"
I'm a little confused by your post, and I think you might be a little confused about what Print Booklet does, if you are using Print Booklet to print the file. Are you?
Your layout should be a multiple of 4 pages, which it is. In the Pages panel you should be seeing the first and last pages as singles, the rest as two page spreads. Is that what you see? If not, please post a screen capture of the pages panel so we can figure out why.
From here, there are two ways to print the booklet as spreads. You can use the regular print dialog and check the Spreads box and you should see the first page by itself, then a series of two-page spreads in consecutive order (readers' spreads) exactly aas they appear inthe Pages panel, and finally the last page as a single. This is OK for proofing, but you cannot fold and bind this and have a booklet that is readable in order.
To get a booklet you can fold and bind you use Print Booklet. Print Booklet "imposes," or shuffles the page order into printers' spreads, so that the back cover is to the left of the front cover, and on the back of that sheet there will be the inside front to the left of the inside back covers (in your case pages 2 & 55) for a 2-up saddle-stitch booklet. Perfect binding (glued, like a paperback book) would be a little different in the page order, breaking the book into chunks, but the process is essentially the same. When assembled, the book can be read in order.
It's very important when running Print Booklet, or when printing spreads from the print dialog, that you also "print blank pages" if there are any to maintain the page count and the proper order and realtionships between the pages.