Two situations

Time passed and Gavrael finally absorbed enough information from the books all at once. He immediately left the library, but it was not to catch up with Evie as he promised earlier. He instead, materialized inside their room and laid himself on the bed.

This was also done as per Gavriel's instructions. He had told Gavrael to put himself into a deep slumber and Gavrael just agreed, understanding why he had asked him to do that. They both will need all the time they need to go over the loads of information he had absorbed from the books earlier and to share them with Gavriel.

It would be more convenient as an excuse for him to fall asleep or Evie will probably keep him awake and interrogate him thoroughly about the spell once she returns. Gavrael wanted to cuddle with her again, no doubt about it. But he knew they do not have much time to waste as of now! Time is of the essence as Evie's pregnancy is progressing day after day!