"I couldn't read that book yesterday but I can read it tonight."
Translation:wa'Hu' paqvetlh vIlaDlaHbe' 'ach DaHjaj ram vIlaDlaH.
Klingon is not SVO but OVS (object–verb–subject)
This sentence is made up of two main clauses or sub-sentences joined by the conjunction 'ach "but".
Each of those two sub-sentences has OVS word order: paqvetlh vIlaDlaHbe' "I could not read that book" is OV and vIlaDlaH "I can read it" is V, neither of which contradicts OVS.
The phrases wa'Hu' "yesterday" and DaHjaj ram "tonight" are time expressions -- not a subject or an object -- and occur at the beginning of a (sub-)sentence.
The order of the two sentences joined by a conjunction is the same as it would be in English, e.g. ABC 'ach DEF is "ABC but DEF", not "DEF but ABC".