Instead of going on a grand adventure, the protagonist wants to bring the joy of books to the strange world she finds herself in.

It unfortunately starts to have more political intrigue in later seasons, but the first season definitely deserves to be on this list.

Warnings:  None

Very cute, and I found it better than Reincarnated as a Slime (it actually predates that anime, too).

Warnings:  None

A very chill and relaxing anime featuring a protagonist who actually has a brain and isn't a pervert or have a harem (rare for an isekai, I know)...and Sui must be protected at all costs.

Warnings:  None (though it might make you hungry)

Yes, this is considered 'isekai'.  While not so much a 'fantasy' setting like most isekai are concerned, it still deals with average kids being flung into a mysterious world completely different from their own.

Warnings:  None.

Light hearted and fun; this anime is actually extremely interesting but very overlooked.  If you want a lighthearted isekai anime to watch, this is a good one.

Warnings:  None.

Though very heavy into political intrigue, this anime explores what would happen if a portal to a fantasy-esque world just opened up in the real world.  This might be a little boring to some viewers as there is a lot of dialogue and political antics, however.

Warnings:  Some blood, political intrigue

The characters are interesting, there are dire consequences of the world, and it's the closest to what it means to start from the bottom. 

Warnings:  Blood, violence, death.  Also, no conclusive ending.

Odd one to add, but it has comedy and starts to add in a plot as well halfway through or so.  The fight scenes aren't that great, but the rest makes up for it.

Warnings:  One-sided shounen-ai (in case that bothers anyone).

Same reason as the first two seasons (both of which confusingly crammed together as just 'Kyo Kara Maoh!'), though this season's plot is much more involved.

Warnings:  One-sided shounen-ai (in case that bothers anyone).

Old, but a gem; this is probably the number one anime I'd recommend for this genre.  Although none of the protagonists are gamers or geeks like today's isekai anime, this one is beautifully done.

Warnings:  Blood.

Not the 'best', but an interesting concept with interesting characters.

Warnings:  Blood and missing limbs.

Sort of a reverse isekai which also makes the viewer flip their views of good and evil during the final couple episodes. Mostly, it's just a light-hearted comedy and slice of life anime.

Warnings:  Occasional blood (nothing even remotely graphic), and some scenes of a girl comparing bust size to another girl.

Comedy with a plot, and each season brings something fun to the table. 

Warnings:  Adult content!  Though there is no explicit content, bust sizes are a thing.

Take comedy, an OP protagonist, some weird followers, and mix.

Warnings:  None

An isekai anime which actually isn't a harem!  It's mostly comedy, but surprisingly starts to gain a rather decent plot; and despite its growing cast of characters, it manages to make all of them stand out in some way.

Warnings:  Caim Kamui is a pervert, and there are some mild succubus antics, but otherwise none