Измените в вопросительное предложение We were reading a book yesterday evening задавая вопрос на разные слова, то есть должно получиться около 6 предложений. Предложения менять в Past Perfect Continuous!
Had we been reading a book yesterday evening? when had we been reading a book? what had we been reading yesterday evening? who had been reading a book yesterday evening? How long had we been reading a book yesterday?