We study a simple epistemic logic with a restricted language where formulas are boolean combinations of (epistemic) atoms: sequences of 'know-ing whether' operators followed by propositional variables. Our language is strictly more expressive than existing restricted languages, where atoms are sequences of epistemic operators and negations followed by propositional variables (in other words: atoms are epistemic formulas without conjunctions and disjunctions). Going further beyond existing approaches , we also introduce a 'common knowledge of a group whether' operator. We give an axiomatiza-tion for this logic and show that the model checking and satisfiability problems can be reduced to their classical counterparts.