Hello! :)
First of all, your game is lovely - the music's fitting for the ambience, the graphics add a certain mystique charm to the setting, and the overall environment is just sooo enticing! I've played a lot of this 'serve-customers' kind of game, but honestly yours is for me more captivating than the ones I've played before (well, I love RPGs and the setting's perfect for my taste :)
That said, I think there might be a few things that would make it even nicer:
Background vs. sprites
Though both are nicely set at the same theme and setting, I think the contrast between the 8-bit sprites and the smooth background layer make the overall graphics seem a little out of place... perhaps if both were pixelated, or the sprites were a little more smoothed, the final result would blend together better. Also, there's a difference in sizes comparing the standing couples and the same ones when they are sat down. Also, the orders' numbers are also a bit out of the overall graphic setting you conceived for the game - perhaps if the number boxes were like small book covers?
Instructions & Gameplay
As I said, I've played a lot of games that involve guiding people to seats and serving them... so at first I just skipped the instructions and went right into playing. But then, I got a little confused. Clicking on the couple added points, like a clicker game, and well, after escorting them to the table I didn't know what to do next: Are the orders taken automatically? And, after they are at the counter, do I have to go back and forth, counter to tables? Or do I press the numbers in my keyboard and they get delivered to their tables? After resetting and reading the instructions, I still couldn't understand some of these mechanics well. But in the end I managed to have the orders set and the tables, tidied up.
Further gameplay
So, after having some orders done, I felt something amiss - some motivation to keep playing on! Perhaps if there were some upgrades, like a spell to tidy up tables, or some magical books that gave other powers, would add to the gaming experience. Interacting with the cat would also be a nice touch! There could also be more 'levels', perhaps after a while the player could move to another 'floor' of the library (with more tables, or more demanding readers)
As I said before, don't take me wrong - I really loved your game. My suggestions are meant for improvements of something that is already good by itself. Feel free to DM me in case I could be of any assistance (graphics, level system, calculations, all but programming lol that's not my turf), this game's really something I would love to see even better :)