第一个用that代指前文的He got hie first book published
而this通常代指后文出现的
第二个不是强调句,若是强调句的话,把it is…… that ……去掉之后,还可以是一个完整句,比如:It was my father who did the experiment in the lab yesterday evening
去掉之后是一个完整句My father did the experiment in the lab yesterday evening
而此处若去掉的换就缺少主句,it代指的是已经提过的时间time