My old book light came with a few light temps and brightness options, but the dimmest setting would still spread light across the room and wake my wife up if i was reading late at night. I made this update to have a more handy, concentrated light for reading. This is a super niche use case but i figured it may come in handy for someone else. I used a pair of 2mm screws and the rest were all 2.5 mm screws. I printed the shell in PLA and clear PETG for my lens. 

It has a clip to use as a bookmark, i kept the adjustable buttons and added a lens to better diffuse and dim the light. 

Link to the booklight i used for internals

https://a.co/d/4erbpbz

I had to desolder the led to take it out of the old shell and the battery wires were just a tiny bit too short for me so i did have to solder it all back together. Other donor lights may fit better without soldering though!