Sorry to hear that the story was spoiled for you. 
We generally disallow spoilers within a short period after a new Halo game is released, so if you stick around these forums, hopefully the same won’t happen to you with Halo 5. :\
It’s hard to predict whether you’ll like Halo 4, even if we know what you thought about previous games. Many people that hated Reach hate Halo 4, yet many people that hated Reach enjoy Halo 4. I’ll try to give as balanced an assessment as I can:
To get one thing straight off the bat: Halo 4 is a good game. It’s not the best game, or even the best game in the Halo franchise, but it is a good game. It has its flaws and it has its strengths.
Two of the larger issues? Custom Games is missing content, gametypes, and settings, and Forge was badly damaged. 343i has taken some steps to fix these issues – mainly the release of Forge Island, a free DLC map that offers an unprecedented level of control to Forgers – but many people (understandably) feel that that’s not enough. The bottom line is that Custom Games and Forge haven’t gotten the attention they need.
The core multiplayer is a different story: though it has also gotten worse in some ways, it’s gotten a lot better in other ways, and it’s receiving updates to make it better still.
Several of the new-to-Reach game mechanics have been improved upon; most Armor Abilities have been nerfed or require more effort to use successfully. Base movement speed has also been improved; Sprint remains in the game, but non-Sprinting movement is closer to Halo 3 than to Halo: Reach. One of the more notable downsides to multiplayer is that weapons on the map have been replaced with semi-randomized Ordnance Drops, and many game modes also give players Personal Ordnance – the most apt comparison for this would be Call of Duty’s “Care Package” – both of which significantly decrease the influence of map control on a match’s outcome.
As with Forge, 343i is taking steps to improve the Multiplayer issues where they can. They recently patched in a subsystem that will allow them to make weapon balancing changes without a Title Update, and they have been working on a set of changes to release, documenting their progress in Halo Bulletins.
EDIT: So as I said – whether or not you like the game is likely to vary. It depends on what specific things you enjoy, what specific things you can put up with, and what specific things you can’t stand. Maybe the Custom Games issues will put you off the game, or maybe you’re a Matchmaking guy at heart. Maybe Ordnance and the decline of map control will bother you; maybe the faster movement and nerfed AAs will make up for it; maybe, maybe, maybe. :\