The main reason I write these reviews of first issues is to see what each new #1 presents and give my opinion of whether or not readers should follow the series. "Avengers World" makes this simple for everyone; have you been reading Jonathan Hickman's "Avengers?" Do you wish to continue? Then read "Avengers World."
This is a third Avengers ongoing to add to Hickman's long-form Avengers epic, only with additional writer Nick Spencer to help lighten the load. Otherwise, there is no difference thematically between this and the main "Avengers" title. All the characters and plots are from the other big "A" book, so this isn't new-reader friendly in any way.
It's not a bad issue though. Hickman always plots out amazing stuff, ranging from street level to crazy galactic war like we saw in "Infinity." However, sometimes it can get buried in the sheer amount of things happening; In this oversized #1, Cap and Bruce Banner meet with SHIELD while crazy horrible stuff happens all over the globe. Various teams are dispatched to deal with each. You may want to see Hawkeye and Co deal with a City of the Dead, but here's Wolverine dealing with Madripoor riots. Almost the entire massive roster gets a panel or two, so get used to shared screentime between plots and characters. Iron Man's "New Avengers" lineup isn't mentioned, so we'll need to see if all these threads are followed up in this book, or if this is sort of the new main book all the others get their start from.
Stefano Casseli adds his usual vibrant, animated pencils to the book, but considering the size and frequency these have been coming out at, he might not be on for long. Count on most major Marvel titles rotating art crews with few exceptions. Spencer and Hickman work well together in that you can't really tell when one is carrying the work and the other is holding back, though some of the dialogue is clumsy; at one point, Starbrand interrupts Hawkeye to talk about how great some bread tastes.
There isn't much else to say about "Avengers World." It sure is an Avengers book. It has superheroes, action, and sets up plots. But again, it's not new-reader friendly in the least, so unless you're willing to catch up with Hickman's run up to this point, I wouldn't invest at this time.