I felt the same way about Ashes. Neat, but I couldn't play it for longer than 20 minutes per session without getting bored.
*addsafterglowbackonthelist*
You mean you haven't played afterglow yet? In comparison to episode 1 it's much bigger, there are about 18 maps now and they are bigger in size and have more variety to them: there's the usual stuff with abandoned settlements and junkyards, but there's also stuff like gardens, forests, military bases, even a football field and the secret level is a haunted soviet submarine, also there's a hub system and you can backtrack to the maps you've already visited.
There are way more dialogues and lore dumps, there's a weapon upgrade system which allows you to turn a sawed off into a three barrel shotgun or put and underbarrel grenade launcher on an assault rifle, that sort of stuff. The arsenal itself has been expanded a bit, they've added an assault rifle, a P.I.G. which is a weapon you have to build from parts you find throughout the game and a laser gun, which is a semi-joke secret weapon, oh and your bike will get a pair of machine guns installed on it. There are new enemies like mutants with shields, mutants with muskets, new ghost type, bigger spore bags, carnivorous plants, new boss etc, the raiders got visual redising as well as new types among their ranks.
Exploration is way more important now, there are more sidequests which reward you with supplies and information, for example the P.I.G. weapon I mentioned or the submarine level, which you can't get to unless you find one of secret areas in the earlier parts of the game.
There's more variety to the gameplay, previously you had action oriented maps, a huge map meant for bike riding and a spooky underground, now there are more horror themed maps, there's a pitfiend race, road rash game on arcade cabinet, a "find the exit before time runs out" sequence, a dialogue minigame where you can convince a mutant to sell you stuff for cheap and may be something else that I can't remember at the moment. The combat is still easy, but it's not terrible, if you are alright with combat in Blood or Duke Nukem 3D then you'll be fine.
Check out my screenshots to see some of the maps. I highly recommend trying out afterglow even if you didn't like the first episode. Make sure to set "sector light mode" to dark or something similar in display options, otherwise some of the sections that are meant to be dark and spooky will be very bright, which will ruin the atmosphere.