Obviously they put the storyline in the "now" instead of the late 1800s. A lot of the scenes had to be updated for the times, like the ferry boat instead of paddle steamers, adding shields on the tripods (a nod to the 50's movie version) to compensate for the more powerful, modern military. The whole scene with the crazed mob and the gun and the only working vehicle was thematically the same as the crazed mob in the book trying to escape London by any means necessary (the main character's brother helps fend off robber's trying to steal a carriage from two women). Different, but the same... the main point was that everyone's out for themselves in a time of crisis, and would do things they normally wouldn't do in order to survive.

It was pretty cool for Speilberg to use the shaky documentary camera style shooting and feel, following just Tom around, as in the book the whole tale is from the P.O.V. of the main character and doesn't cut away to anyone else nor is there a bird's eye view of it all. All outside information was gleamed from others "I just got back from such-and-such town and the whole place is on fire, don't go that way! etc.". The story is basically about the main character just trying to survive the impossible, and pretty much unable to fight back (the whole bomb up the yazoo was made up for the film, gotta throw in a heroic moment for Tom, I suppose).

Speilberg just had to add a couple of kids to tag along with the main character. Both the book and this movie share a wife (or ex-wife in this case) waiting back in the (supposed) safety of a town. I can let the kid surviving in the movie and show up for the "happy ending" slide a little because the main character in the book thinks his wife is dead from a report that the town she was staying in was completely destroyed by the tripods, and she shows up at the end, unscathed.

The three of the book's characters were combined (The Artilleryman/The Curate/Ogilvy) to make Tim Robbins character, Ogilvy. All that "boring stuff" in the basement (as I've read user reviews complain about) with the aliens probing around, Tim's character going crazy (Artilleryman/The Curate) with Tom's character killing him (which happens to The Curate) to shut him up so the aliens wouldn't find them, is in the book.

The movie aliens were from "outer space" instead of Mars, which kind of screws up the whole Red Weed thing (it's what makes Mars red). It still made for cool visuals, though. Also, in the book, the aliens were shot out from Mars, one by one, in giant metal cannisters towards Earth, not buried underground, with the aliens beamed in. Minor nitpick I suppose, as it doesn't really change the story overall. The alien designs are way different (more regular looking, bland aliens as opposed to the giant brain squids), and they are unaffected by Earth's gravity (since they aren't from Mars), but the Tripods were spot on. They didn't use The Black Smoke (black poison gas cloud in the novel), which is the only change.

The ending is the same, thankfully Tom didn't take over a tripod and start fighting against the rest of them in some big Hollywood climax. It's cool that the narration at the beginning and end are pretty much straight from the book.

Common, every day bacteria; the kind humans built up resistance to thousands of years ago.