Nuance of かと思えば in this context


> 敷石ぐらいの大きいな革製本、シルクの表紙で切手くらいの大きさの本もあり、奇妙な記号ばかりの本がある **かと思えば** 、何にも書いてない本もあった。  
>  There were leather bound books as big as paving slabs, silk covered books
> the size of postage stamps. There were books with nothing but weird symbols
> ???? There were also books with nothing written in them.

It seems that Xがあるかと思えばYもある means 'There is not only X but also Y'. What
nuance does this construct have? In what situations would it be used? How
would it differ from だけではなく, for example?

I'm guessing from 思えば that it invokes some element of surprise/wonder?




`Aかと思えばB` expresses a psychological **sequence** of observations. This is a
common pattern used to express that this person noticed one thing after
another in a short period of time ("Oh it's A, and oh, it's B, too!"). The
same construction is used to describe one event actually happened right after
another, for example, 彼は部屋に入ってきたかと思えばすぐに出ていった (He left the room right after (I
noticed) he entered it).

`AだけではなくB` simply means "not only A but also B". This construction puts
emphasis on the B part (B is usually more surprising/relevant/important). On
the other hand, in `Aかと思えばB`, B is something that happened (or was recognized)
right after A.




`Aかと思えばB` expresses a psychological **sequence** of observations. This is a
common pattern used to express that this person noticed one thing after
another in a short period of time ("Oh it's A, and oh, it's B, too!"). The
same construction is used to describe one event actually happened right after
another, for example, 彼は部屋に入ってきたかと思えばすぐに出ていった (He left the room right after (I
noticed) he entered it).

`AだけではなくB` simply means "not only A but also B". This construction puts
emphasis on the B part (B is usually more surprising/relevant/important). On
the other hand, in `Aかと思えばB`, B is something that happened (or was recognized)
right after A.

