yes, you can read using the threecandle lantern. If it's fairly close by. I set mine up with a reflector if I'm going to read. Have had the single candle lantern for decades. bought the threecandle a few years ago. love it. puts out a LOT of light on a dark walk to the outhouse

also gives off a fair amount of heat. more than enough to heat up a tent.
as to making your own candles, 2 ways to do it: measure the diameter of the candle, buy a pvc pipe the same diameter (interior diameter of the pipe). 2nd way would be to dip candles. just keep dipping until they fit the size.
I'd suggest beeswax in a 50/50 mix with commercial candle wax. burns longer, and smells great. might want to test a couple tho...the candlelantern is a bit like a container candle...the wax melts inside the lantern and forms a bit of a pool for the wick to soak up. more of a pool than a straight candle does.
ahha! I see they sell a 100% beeswax candle for the lantern. there's my answer about the 50/50 mix. guess it will work just fine. I like the 100%beeswax even more

should burn up to another 50% of time.