Meteors have hit some cities in Southern California. (I can't remember if they were large like San Diego, or Los Angeles, or if they were smaller cities like Bakersfield or Fresno). The protagonist (High School? age at the time) who was out of town at the time, has lost all his family and friends.
Now 5-10 years later he is working in a electronic repair shop. Someone brings in an old broken game system (like Nintendo or Sega) that he had in the garage that his kids want to play, to see if he can fix it. But he was not expecting much as it was in pretty bad shape. The protagonist repairs the circuit board, rebuilding part of it and re-encoding the operating system chips (flashing the ROMs with rebuilt codes that he wrote).
The guy is amazed, and brings him some other tech parts to see if he can get them working, or figure out what they do. The protagonist eventually concludes that something is very strange about the tech parts he brings in. He figures out what they should be for, but they can't possibly work as designed, something is missing in the circuits. He concludes they must be alien or future tech.
Two special things I remember about the Protagonist.
He had mental health issues. (Maybe from the breakdown from losing his family? or he is bi-polar, or schizophrenic). His long time psych doctor has had him on various meds and he definitely has episodes during the story, requiring changes in his meds which don't appear to be working as well anymore.
Because his home town and all his family and friends and ID records were wiped out by the meteors, (he was too young to have an ID at the time) doing background checks is VERY difficult. The man bringing him the tech wants him on the team trying to crack the function of the devices, but there is problems getting him clearance.
If I recall correctly, this is only the beginning of the book, 5-6 chapters, certainly less than half the book, I don't recall what happens in the rest of the story.
The tech devices were strange, like one might have been a storage device with an input rate of 10 terabits/second but the storage volume was only 1 meg. It was like trying to fill a drinking glass from Niagara Falls. What's the point. I think it was eventually concluded that the "storage volume" was actually a portal to somewhere else. (More like a Stargate as opposed to another dimension).