difference - "had they known" or "if they had known"

Can this:

These same officials, however, would have been appalled had they known what was going on behind this façade of self-help.

be rephrased as

These same officials, however, would have been appalled if they had known what was going on behind this façade of self-help.

?

Answer

The rephrasing is fine, however, the first leans towards the formal stylistically.

In general, the hypothetical if clauses (if + were/had) can be replaced with the construction "had/were (subject)."

For example:

"If I had known, I would have acted sooner" -> "Had I known, I would have acted sooner" "If he were taller, he could reach the ceiling" -> "Were he taller, he could reach the ceiling"

There are stylistic issues that make some replacements sound awkward and stiff.