And - remember each page of the final booklet not only has a reverse side, but it also joins to a page with a reverse side at the opposite end of the booklet e.g. in a 6 page booklet page 1 & 2 are the same sheet as P15 & 16. You might deliberately leave a blank sheet but be aware that you need to work in groups of 4 pages.
Also find out from your printer how many pages will fit on one printing plate. You might find (for example)that 24 A5 pages will fit on one plate, but if you want 28 pages it will need a second plate (extra costs), but up to 48 pages would still be just two plates.
You really do need to discuss with a prospective printer, because these sort of details can be important to the final price you will have to pay.

Another important factor is how many copies you want to produce. Using a printer is expensive. If you want a simple booklet in small numbers it can be cheaper to use photocopying and staple them together by hand. If you need large numbers, there is a point where printing becomes more economical. A few years back we reckoned in the UK that the crossover point was around 500 copies. Less than 500 worked out cheaper to photocopy.

Obviously, professional printers will produce a more consistent and neater product, but it depends what you actually need. A photocopied booklet can be made as and when you need extra copies, so you can use income from one batch to pay for the next batch.

Quack!
GtD.