Describe the bug
The README claims that Reader::CommonLisp treats special atoms specially:

SXP::Reader::CommonLisp.read %q((or t nil))          #=> [:or, true, nil]

However, in practice, Reader::CommonLisp doesn't map Lisp t and nil to Ruby true and false; it just treats them like any other atoms and converts them to Ruby symbols:

irb(main):008:0> SXP::VERSION.to_s
=> "1.2.2"
irb(main):009:0> SXP::Reader::CommonLisp.read %q((or t nil)) # the same example from the README
=> [:or, :t, :nil]
irb(main):010:0> RUBY_VERSION
=> "2.7.1"

I think this is a bug. Either the documentation or the gem should be updated.