I feel your pain man as I'm in a similar boat. I stopped reading anything that requires me to put too much effort into considering the text in front of me. Some days it worries me... like I'm too deep into the daily grind to think anymore.
I've found the older I get, the less time I have for either depressing 'doomsday' novels predicting the downward spiral of the US or 'highbrow' literature where I have to think about every nuance of what I'm reading, study the symbols, devices and take the time to appreciate all the references the authors is throwing at me. Even worse, anything that even remotely gets a bit preachy hits the recycle bin.
I'm too tired, too busy and well.... too old for that highbrow nonsense.
When I was in my teens and twenties, I didn't have a whole hell of a lot to worry about. These days... I got mortgages, bills, deadlines, responsibilities... the worst deadlines I had as a kid were to write ten page papers. Even when I hit the corporate world and got married, stuff wasn't too bad, but it began to get tougher. Toss in a kid, more responsibilities with the job, some rough personal drama, a brush or two with death... after awhile all that stuff piles up on you and you are wandering around like Atlas. When I want to relax, I pick up something lighthearted and fun where I can be entertained.
Life is tough. Whether you are riding high on a pile a wealth or grinding gears inside the machine somewhere, its not easy being green. It's hard to tell yourself you are relaxing with some weighty tome when 90 minutes previous you pulled over on the highway to staunch the flow of blood from your nose because you are stressing about the deadline looming, your next review or something equally stressful. Picking up a book where you have to work at enjoying it fully after having been stressed out for the last 12 to 14 hours.... for me, that's not happening anymore.
A lack of time is the biggest culprit for me. I find that I still love to read, but epic novels or literature where I feel like I need a pipe, some brandy and lounge full of people to bandy the ideas back and forth.... those things are gone along with my Lego's, starwars figures, underroos and varsity jacket. When I read now, I'm brandishing a staff with Harry Dresden or telling Sookie she's asking for trouble or I'm fishing out my glock to cover some random ex-cia/fbi/nsa agent in the latest secret agent book. When I'm reading now, it's gotta be something I can grab a chapter of here and there while I'm running between places or right before I go to bed.
Audio fiction? It's my new drug. My commute is a solid hour of road raging assholes. To survive, I'm mainlining PodCastle and EscapePod on my way to work in the morning and on the waoy home at night. Any drive over 15 minutes is when I start queuing the minis.
On the nights where the kid is in bed and the wifey is out with some friends I guess I could pick up something to stimulate the old noggin, but more and more I find myself wanting to create my own stories. Tell my own tales. Sure, they are horrible scribblings of a madman, but when it comes to entertainment, the joy I get from me scribbling a bunch of bullshit on a computer screen is vastly more entertaining than anything the TV can throw at me. Well, except when Mythbusters is blowing shit up in the name of science. If I can have mythbusters on in the background while I'm writing, beer in front of me with some cheese and crackers... I'm in frickin heaven.
Crap... this brain vomit got way too long.... almost out of lunch break.
In closing man, don't get down on yourself for not reading the stuff you used to devour or for not taking the time to rise above our monkey and lizard brains. Stuff happens. If you really want to excercise the brain, then just make the time for it and force yourself to smell them intellectual flowers.