EPs

I'd say EP:s differ quite a lot. Sometimes (mostly before) it is just a single with extended play, so maybe the hit single and 3 remixes or 3 B-sides. Sometimes it's a standalone EP that's released in between albums with 4-5 songs that might just be released on that EP exclusively. Sometimes it's more like your example where it's maybe 3 songs from the forthcoming album and maybe a bonus song which is not or that all songs on the EP will be on the album.

Back in olden times EPs used to be 10" vinyl discs that ran at 33 1/3 RPM. Nowadays basically if an artist says it's an EP than it's an EP. So you get stuff like this



Which is almost an hour long but gets labeled an EP anyway.

Yeah some bands definitely have some essential ep's.

Alice In Chains - Sap & Jar Of Flies
Nine Inch Nails - Broken
The Dillinger Escape Plan - Irony Is A Dead Scene
Baroness - First/Second/Third
Meshuggah - None/I

A lot of Hardcore Punk bands from the early 80's released fantastic ep's but eventually released them in compilations.

^
Like mini-series, used to be a mini-series was 4 days, now they say 2 are.

E.P.s were also used as gap albums {See 5.89 EP, G'nR Lies} Until the next record was released/ready.

Lies is an EP.
"Live ?!*@ Like A Suicide" was released 7 months before Appetite and was tacked on the b-side of Lies. They only pressed 50,000 copies on cassette and vinyl, and few people knew it was out there.
4 new songs, though 2 were acoustics of Appetite songs.

Only thing this band ever released. John Garcia's first project after Kyuss broke up. Imo a great EP, I listen to it often.

I don't think there's much point sticking real closely with the old definition of EP. Things change. A double album used to be an album spread across two vinyl discs; now it's an album spread across two CDs, so many albums that would have been double albums in the '70s are just considered regular albums that happen to be kind of on the long side.

I love Paradise by Lana Del Rey as well.

Is this one with the Sabbath Cover (Snowblind I think it was)?

EDIT - Yes, but Sweet Leaf not Snowblind

Also, there's no official cover, but Scarlet's Hidden Treasures by Tori Amos is ace as well.