Lewis has had to make a great many assumptions to write the book, because if he hadn't the thing would be the size of a library. But let me back up for purposes of this conversation and undo two assumptions: 1) That all modern technology will necessarily decay away post-apocalypse. And 2) That all technology HAS to necessarily decay away on the recovery timescales discussed in the book.
Let me unwind the second assumption first. We tend to think of our modern contrivances and gizmos as disposable, and to some extent they are. I've been through 6 cell phones in 10 years, I have 3 tablets and 4 computers currently in use, and I have no expectation that any of it will be usable in 10-15 years, let alone actually used. Those devices, though, are a product of a certain market and design ethic. We as a global community have demanded cheap, powerful electronics and the shiny toys they underpin. The market has responded with semi-disposable gear of all kinds.
But what if the chief requirements of an IT architecture were not cheapness and power, but reliability and longevity? Could we build an IT system / architecture that could run continuously for decades with 99.999% reliability, and be powered down for centuries and still be rebootable? Could we build a storage capacity in an IT system to reliably store, say, 10-100 TB of information in a non-volatile format for 1,000 years? Think miniaturized magnetic core random access memory, but on steroids. Can I make a microprocessor (even a macroprocessor) that can survive and operate after centuries of being turned off? Remember, running the graphics performance of the latest FPS game is NOT a requirement. I need to serve information to an interface / interaction device at about the rate a human can comprehend it, so the latest 802.11 chipsets and GPUs are wasted on this project. And can I build a simple foolproof interface device that can survive for centuries?
Not to belabor the point, but I think if we thought about the requirements correctly we could build (and proliferate) IT systems that could last a heck of a long time, and store a very large amount of insanely detailed and useful information.
Are there current systems in what we might call the mainstream IT world that can last? I've been trying to ask this question with regard to DVD storage, and that led me to the Taiyo Yuden CD/DVD solution. These things, and some competitor products, are supposed to last 100-300 years. Gold layers and special dyes are supposed to be the trick. I imagine you can expand their longevity even further through very careful climate control, and UV exposure and oxygen exposure control. They may go substantially longer if you store them in the dark, in cotton sleeves, in a nitrogen atmosphere. What about the players? They are probably the weak link, as is their dependence on electricity. But maybe simple improvements to the players could radically expand their useful lives (i.e. get rid of all nylon gearing in the mechanisms!)
Bottom line is that we may already have some IT technology out there with some longevity and storage capacity, and we could certainly specially-build IT systems for reliability and longevity, and scatter them around the planet.