Well, I won't lie to you: the art is the draw, here.
Sure, the story by Christos Gage is perfectly solid. It details four encounters between the X-Men and Spider-Man, with many years separating the events of each issue, a nefarious plot by Mr. Sinister tying them together. He wants their genes, don't you know.
And it's kind of neat to see the four-issue mini-series nimbly slide through established continuity, referencing events, plotlines, and costume changes without being weighed down or overwhelming. Gage has a good handle on the characters and makes sure to bring in some interesting baddies from the rogues galleries of both Spider-Man and the X-Men.
But as I said, if you are going to buy this, buy it for the dazzling art. This is Italian Mario Alberti's first major work on this side of the Atlantic. (He's done some covers for DC.) Prior to this, he worked on two separate series for French publisher Les Humanoides Associes, the very same publisher that Jog and Tucker Stone currently are examining with a microscope (I'm sure they'll get to him eventually).
Alberti, who does the pencils, inks, and colors, breaks out the whole toolbox here. His action scenes are terrific, using nifty perspectives:
and knockout two-page spreads:
Though this mini-series really is just a collection of action scenes, strung together by a fun little plot that knows enough to get out of the way of the art, I liked it.
You can order the collected edition from Amazon here: X-Men/Spider-Man HC (Note: the collection's size is 128 pages because it includes a reprint of X-Men #35.)