"Měla to být velmi dobrá kniha?"

Translation: Was it supposed to be a very good book?

[MandelSoft]

Why is this answer wrong:
"Should it have been a very good book?"

[Pollyhs]

what about should it be a very good book? for "Měla to být velmi dobrá kniha?"

[AgnusOinas]

"It should be" translates as "Měla by to být..."

[Pollyhs]

Thanks.