The only time the game forces you to reload and tackle a battle again is during escort missions, of which there are rather too many. Here you'll find that enemies are reset, but your weapons and items are not. Use up your Molotov cocktails and break your best weapon in a failed attempt and you'll have to try again with those handicaps already in place. Hoping for a herd-thinning fury attack is the only way out of this cycle of inevitable failure.
Elsewhere, you can see how the need to work around the requirements of co-op play has boxed the design into awkward corners. The game has no manual save, so once the story is completed there's no way to go back and finish off any quests you didn't tackle. Like an elderly driver navigating a tricky roundabout, all you can do is start over and go around again, playing the story from the beginning with your items and player level intact.
The sense of escalation, at least, is well handled. Enemies level up alongside you, so that encounters with zombies remain tense and challenging right up to the end. The engine clearly can't render more than 10 or so at a time, certainly nothing to compare with the crowds of Dead Rising, so this seems like a reasonable compromise. Loot drops are typical of the genre, and combined with the impressive modification options ensure that the drive to constantly improve and add to your arsenal provides compelling momentum even when the game itself struggles.
Co-op play makes the engine work harder, resulting in some hilarious puppet-like animation, but it works in a rudimentary sort of way. Players in the same game are free to roam the map, tackling different side quests, but story progression and fast travel demands all players gather at the same spot. The matchmaking system works not on player level but chapter checkpoints, putting you with players who are at roughly the same place in the game. Progress is automatically saved should other players quit, and your solo checkpoint is restored. It's a clunky and graceless system, but mostly workable and the game is considerably more fun with a full complement of players.
I didn't encounter anything game-breaking in the 26 and a bit hours it took to complete the story solo, or during my forays into co-op play, but it would still be all too tempting to fill this review with complaints about the flaky game engine, the weird floating objects and distracting animation spasms, and annoying glitches like inactive quest points, inconsistent navigation markers and the general air of a scrappy half-finished game. All that stuff is in here, and can easily dominate the experience.
I'd be lying if I said I didn't enjoy the experience though. Dead Island is a deeply flawed game, but it's also clearly a low-budget game and one that has interesting ideas, often under-served by the bargain-basement code. Finding the diamonds in the rough demands a lot of patience, and enough investment in the base joys of zombie slaughter to tolerate the laundry list of flaws.
I suspect this will be one of those games that will be justifiably mocked by the majority for its many flaws but embraced by a forgiving minority, and passionately defended for its underdog status. Neither response will be entirely wrong. Much like gnawing on human flesh, Dead Island's clumsy horror-action role-player is the definition of an acquired taste.