Around 60-70% of English comes through French (iirc). If you know the general rules, you can have a couple thousand words in your French vocabulary immediately. For instance, words ending in -ation are all identical in French (with 3 exceptions). Words ending in -cal (e.g. "political") just switch to the -que suffix ("politique"). Words ending in "-able" are often also the same.
The same expression exists in Portuguese, so I'm just guessing the meaning here, but when you say "à part" it means being out of a group, separated. In the case of people, it usually means they're not like their peers, therefore odd (like the expression "you are something else"). In other cases, it usually means something is separated, or must be done separately, bought separately, etc.
The situation I imagine is that you're at a mall buying a bunch of stuff, and while you're paying the cashier says "les livres sont à part", meaning you must pay for them separately, or they're not part of the discount you're getting for the other objects.
It would be good to get the opinion of a native speaker though.
"les livres sont à part" exactly means: the books are in a different place (separate from other stuff), including in a figurative sense, like: "la TVA est de 19,6% sur les articles vendus ici, mais les livres sont à part avec une TVA à 5%" (the VAT rate is 19.6% on all items sold here, but the books are "à part" with a VAT of 5%). Knowing that, you can translate (in real life) as you think is best.
"The situation I imagine is that you're at a mall buying a bunch of stuff, and while you're paying the cashier says "les livres sont à part", meaning you must pay for them separately, or they're not part of the discount you're getting for the other objects."
Then, my question to the moderators...
When we have to pay for things separate, we usually say "They are separate" in English.
Can we translate this then as "The books are separate"?
The dropdown lists are purely suggestions for possible translations of a word. There is no connection implied to the sentence in hand. In few cases will all the "hints" work in the same sentence, and in some case, none will.
Think of all the different possible meanings for the English word "bank", for example - a financial institution, the ground next to a river, an array of lights, a shot off the side in the game of pool.... In any one sentence, no more than one would be the correct meaning.