That I couldn't identify her was no more a surprise than that she should know me

Question

I found this sentence -

That I couldn't identify her was no more a surprise than that she should know me.

What is the meaning of this sentence?

Source - The Hungry Tide by Amitav Ghosh

Answer 1

Analyze it thus:

A was no more X than B [was X].   (the piece in brackets is implied)

This means “A was X, but B was X, too, and A was not more X than B.”

• A is the proposition “I could not identify her”, transformed into a subordinate that clause so it can act as the subject of the sentence.
• B is the proposition “she should know me”, transformed into a subordinate that clause so it can act as the subject of the clause which is the the complement of the more .. than comparison.
• X is “a surprise”. A is a surprise may also be expressed A is surprising.

So you may paraphrase it:

It was surprising that I could not identify her. But she knew me, and that was just as surprising, perhaps even more surprising.

Answer 2

Although the precise meaning can only be certain only within a specific context, a good approach to deal with complex or long sentences is to dissect it into parts. (I usually call this "bracketing" or "parenthesizing".) Just like the way I did in my answer to one of your previous questions.

Here is how I would bracketing your sentence,

[That I couldn't identify her] was [no more a surprise] than [that she should know me].

Bracketing can help us to see parts of the sentence clearer. To do bracketing, we must first be able to identify the main verb of the sentence (or the clause). Most English sentences (and clauses) will have a straightforward arrangement of (subject)-(verb)-[object]. (There are some variants, but this is the main construction.)

If you can identify the main verb correctly, most of the problems are solved. This is because the part before the verb must be the subject of the sentence. And the part after the verb must be either the object or the complement of the verb.

Back to our sentence again,

[That I couldn't identify her] was ([no more a surprise] than [that she should know me]).

The verbs in the sentence are "couldn't identify", "was", and "should know". A quick look at them can tell us that "couldn't identify" and "should know" cannot be the main verb because of they are part of that-clauses ("That I couldn't identify her" and "that she should know me").

Knowing that was is the main verb make it easier to reduce the whole sentence to:

X was no more Y than Z,

where
  X ~ That I couldn't identify her
  Y ~ a surprise
  Z ~ that she should know me

To understand this, you need a little logic.

[X was no more Y than Z] is a way of saying a few things,

X was a kind of Y.
Z was a kind of Y.
The quality of being a Y of X was no more than the quality of being a Y of Z.

[The quality of being a Y of X was no more than the quality of being a Y of Z] can be rewritten as,

Y(X) < Y(Z)

Putting the original X, Y, and Z back into that inequality, and you will get,

The surprise that I couldn't identify her is no more than the surprise that she should know me.

Of course, you can bracket it,

[The surprise (that I couldn't identify her)] is no more than [the surprise (that she should know me)].

And you still have a sentence equivalent to the original.

And now, with a more specific context, you can get into its deeper meaning easily.