Now in a Toddler Bed...

We always did one of those clip on reading lights with our kids. The deal was they got to have it on and "read" in bed quietly, but no getting up and down, otherwise, no more light.
This was pretty easy because they would have a fair amount of books already in bed with them, and extra books in a basket on the floor. Once they got used to the routine they would turn the light off themselves (in the beginning they sometimes fell asleep with it on, I would just go in and turn it off later.)

This is a new thing for him - having freedom to get out of bed. All toddlers go through this when they get their big beds - they just keep getting up because they can. Once the novelty wears off, he'll go sleep normally again. However, reading books is good for him so I think the timer suggestion was a good one. My son is 10 now, he still sometimes gets up to read if he can't sleep and I have to give him a time limit or he'll be reading all night. Good luck!

Just get a "Mighty Bright" book light.
From Barnes and Noble.
It is good, my kids have it, it is perfect for reading in bed.
It clips onto the book.

Then, put a stack of books, NEXT to him, so that he can peruse it and get it, on his own.
Its nice he likes to read in bed and entertains himself before bed.
Lucky you!
My son, does that too.
Let him, do it.
There it nothing wrong with that.
That is your son's way, of winding down and doing something "calm" before bed. That is great.
He is... going to bed in his new bed, just fine. To me.
He has his own "routine" for bedtime.
Wonderful.
BUT, since his "reading" is going past his bedtime... THEN just put him to bed and into his routine, earlier.
Tell him, that is so that he CAN read and whatnot, before bed, and not waste time, before it gets too, late.
I do that too, with my kids.

I would think a larger night light right near his bed would be bright enough for the "reading" that a toddler does. I actually found when I got one from the dollar store the cute cover that was supposed to dim or diffuse the light didn't do much so I found it too bright, but would probably be great for what you need it for.

Could you maybe get a timer on a small bedside table lamp? Set it for say an hour and let him know that when the light goes, it's time to go to dreamland, where he can meet up with all the characters in the books. That should get him excited for lights out and get his imagination going even more.
You could also have a nightlight that turns on once the lamp goes out, so that he can still see where his bookmark is and set the book down in the right place.
You got lots of great advice.

My dad is a doctor (opthamologist) and has assured me that this reading-at night-with-a-light-on-is-bad-for-you is kind of a myth. Much worse are computer screens. However, of course it will be nicer for the little guy to sleep with a lower light on.

Do a night light or tell him he has so many minutes to read and then the light goes out. That will teach him there are times for certain things and then he does as you ask. I would close the door with a night light on although I usually opened our kids doors when I went to bed so I could hear them better. Up to you though.