Romania

Yes, he's been but hasn't done a dedicated book as, compared to other European countries, it apparently isn't high enough on enough visitor must-do lists yet to make a book economically worthwhile. He recommends (and sells online) the Lonely Planet Romania/Bulgaria guide:

https://store.ricksteves.com/shop/p/romania-lonely-planet

And he's included some info about the country in his Eastern Europe guide:

https://store.ricksteves.com/shop/p/eastern-europe-guidebook

Some random pieces he's done about Romania:

https://blog.ricksteves.com/cameron/2016/12/rse-behind-the-scenes-romania/
https://blog.ricksteves.com/blog/bulgaria-romania-local-guides/
https://www.ricksteves.com/watch-read-listen/video/tv-show/romania
https://www.ricksteves.com/watch-read-listen/read/articles/bucharest-romania-little-paris-of-the-east

More here:
https://search.ricksteves.com/?utf8=✓&query=Romania&button=

http://romaniatourism.com/trip-planner.html

Let us know in what season you plan to travel to Romania, from where you're coming and to where you're heading, and how much time you have available - we can give you some suggestions.

Watch here the Rick's film about Romania: https://www.youtube.com/watch?v=1BK8wJJQiB4