We have the same reading taste, I've read those Ruby books already, I would also recoment the book "Eloquent Ruby".
I use Sinatra for small and large applications, no regrets, it is awesome.
Eloquent Ruby was on my shortlist, it is a good book but I think Practical Object-Orientated Design In Ruby just pushed it out of the top 3. Good to see another Sinatra fan here :)