You can gather what the film was about from the film description and countless online sources. My opinion of the film in brief: Excellent.
Let me tell you about the blu-ray. The film is excellently adapted to the format with great quality and sound. Bizarrely enough though, the film comes with NO commentary.
The extra features: this segment is where Marvel Studios have stood out with all their release (and Marvel with most other films too), but in contrast, the biggest Marvel film to date has perhaps the weakest showcase in comparison. It consists of a little banter and fun with a gag reel, a bit of behind the design fluff with an art reel of the Avengers which doesn't show much of interest, and the best part of the extras, some great yet understandably omitted deleted scenes, a Marvel Studios short film called Marvel One-Shot: Item 47" (an entertaining piece looking at the aftermath of The Avengers, and how a couple who find a Chitauri gun left behind, and use it as a way to make money.)
Where the fail falls in this is my 3 of the 4 favourite expectancies with comic book film releases: commentary, character's comic history, and the making of featurette (the 4th would be the deleted scenes.) To my disgust as a fan, I learned after purchase that the film had none of these... OUTSIDE of the North American release, so all these glorious little features (and more) are available from there only.
Disney (the distributors and Marvel parent company) did an announcement later, and explained they missed a deadline, so they won't bother putting it on blu-ray/releasing another version with these features (at least not in the near future) and actually went on to say buy it region-free from USA. This comes at a much higher cost, and probably (from past import experience) won't allow digital copy usage for the film and soundtrack.
Very, very lame. Film aside, I paid 18 quid for a film and little additional interest to me outside of it (I'm a guy who appreciates bonus features, as a self-confessed cinephile.) There is no real product value and at this price, more is expected.
Then again, if you don't care for that extra juicy stuff that caramelises over the plump piece of well cooked steak, this will be perfect for you (if price isn't a concern.)
Rating: I'll give a star for the film, quality on blu-ray, extras, commentary, and value-for-money. I only gave it two, for film and quality.