When I started to read this, I thought this was from the (more famous) Greg Bear.
On the one hand this is a crime novel in the tradition of the "hard boiled detective fiction". We have the cliché detective who sits in his shabby office and waits for clients. And when one shows up it is this shady character that the detective really does not want as a client, but he needs the money blabla. These are rather tired tropes but they seem down-to-earth and grounded in reality.
On the other hand there is this outlandish idea that there is this little device with which you can save time-slices of your life that you don't need and store them for later. And for that you have to put them in a special kind of bank which stores them on magnetic tape (sic!). There are more aspects of this device. It makes some users feel good, because ... well why exactly? It makes no sense.
This is also a dysutopian novel, where mankind is in sharp decline and everything seems so depressing.
I found this all very uneven, unconvincing and no fun to read. So I quit on page 104 of 300.
To come back to the beginning, it is probably not so surprising that David is not as famous as Greg.