Definitely worth playing 13th Age.
It's my favorite game system at this time, even given my delight in 5e.
Our GM brought our game to the Midgard/Southlands setting for 13th Age, and then tweaked the campaign structure by setting milestones by season: Spring, Summer, and Autumn. Each game session covers one season. Complete all three seasons, and the PCs go up a level.
A game session has 3 major encounters and generally runs 6 hours.
In-game time spent moving from place-to-place or gathering information/supplies, etc., uses a wonderful game-mechanic. The players are asked open-ended questions, such as, "While traveling on the road to Zobeck, Dalioza, some event forced you off the road. What was it?" The next player gets asked about some complicating factor(s) in the situation, and another player gets asked about how it got resolved. Over a session's play, every player is likely to contribute more than once to creating the story as we go along.
We don't always have time to complete the full seasonal encounters during a game session. When that happens, the GM runs a quick "talk-through" where we learn about what was meant to happen. This is our work-around, since our lives prevent us from getting together as often as we'd like, and can sometimes go months before we can find a mutually available date to play.
A group able to meet say, bi-weekly, might well be able to complete the full 1st-10th level protocol in under a year. This kind of rapid advancement was one of the original desires of the game designers.
Every level advanced increases the attack roll bonus and the number of dice rolled for damage and/or other effects. A PC just gets better and better quickly.
There is not really a good option for multi-classing. The best bet is to pick a class and race and stick with it for all 10 levels.
Our GM introduced an optional Winter season that is a 1-on-1 adventure conducted by email between the player and the GM. (He took that idea from the Winter-over in the Pendragon game.) Not every player utilizes the Winter season option, but it does give greater depth to character development, and introduces the potential for taking Feats that are specifically designed for the PC.
Combat: We use miniatures and a white-board laid flat for combat. The GM draws quick layouts of the scene. There are two ranges: either nearby or long-range, and no grids are involved.
Theatre-of-the-Mind works very well for this game system, too. So much of the game, especially the player-contributed story aspects as play goes along, is really geared to TotM.
Minions share group hit-points, allocated equally. Example: If a group of 5 minions has 40 hit points, every time the number of hit points is reduced by 8 hp, that's one less minion.
The speed of combat moves fairly briskly, although real-world issues slow it down sometimes: calls of nature for the players, attention required for the host's pets, time spent searching for an obscure and dimly remembered rule (be it online or hardcopy, but there aren't so many rules that it happens often) or dice that go sailing off the table (too often), food delivery interruptions, etc.. Y'know: the Usual Suspects.
Overall, I like this game a lot. It's not over-burdened with source material and it plays quick and clean.
When I next DM a 5e game, I plan on importing some 13th Age ideas to speed up 5e play.
Our group shares a Dropbox account with all the non-"GM Only" published material and other group-specific information, such as a very short-list of House Rules. Don't really need those too much, anyway, as this game seems to have fewer subjective glitches than most.
All of the source books are available for purchase as pdfs.
