Why is Jonas surprised when he goes into the Annex for the first time in The Giver?

Jonas is surprised because the Annex has books and the speaker has an off switch.

When Jonas is selected to be the new Receiver of Memory, he has no idea what to expect at first. He barely knows who the current Receiver is, and knows almost nothing about the position itself. He is definitely not expecting the assignment.

The Receiver of Memory does not live with the other citizens of the community. Family units live...

Jonas is surprised because the Annex has books and the speaker has an off switch.

When Jonas is selected to be the new Receiver of Memory, he has no idea what to expect at first. He barely knows who the current Receiver is, and knows almost nothing about the position itself. He is definitely not expecting the assignment.

The Receiver of Memory does not live with the other citizens of the community. Family units live in their own dwellings and there are separate living quarters for childless adults.  The Receiver has a special quarters behind the House of the Old, where the elderly live.

The Annex was very ordinary, its door unremarkable. He reached for the heavy handle, then noticed a buzzer on the wall. So he buzzed instead. (Ch. 10)

There is a small lobby with an attendant, who treats Jonas very respectfully. There are locks on the door, which is very unusual in the community. The attendant explains that they are to ensure the Receiver’s privacy by making sure no one will accidentally walk in on him.

The dwelling is a little more luxurious than Jonas’s, and obviously more secure. There are two very significant unusual things about the Annex. One is that it has books, when books are almost nonexistent in the community except for rule books and instruction books. The Receiver of Memory has many books, however.

The other unusual thing about the Receiver’s Annex is the speaker.

It was the same sort of speaker that occupied a place in every dwelling, but one thing about it was different. This one had a switch, which the man deftly snapped to the end that said OFF. (Ch. 10)

The speaker is used to spy on every citizen in the community. It communicates both ways. When citizens need something they ask for it there, and the speaker can comment on things citizens do. Sometimes announcements are made to the entire community that are really directed at one person. To turn the speaker off is an enormous power.  The Receiver is the only one who has privacy.