El libro fue un suceso internacional.

English Sentence

The book was an international success.

This sounds like Spanglish to me. I would use éxito.

The Latin root of the word success is successus, so I think the Latin based languages that preceded English probably have a stronger claim on it and that English is a dirty rotten thief.

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OK, but one has to take care not to use it when it can be understood as “event”.

Addition: FWIW, Wiktionary says: " In modern usage suceso is a false friend, and does not mean ‘success’."

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Perhaps, it’s a very specific secondary meaning of suceso. According to my dictionary:

2 formal
Resultado exitoso de una acción, empresa, etc.: sin duda alguna, la presentación fue todo un suceso.

and the real authority on the subject, https://www.rae.es says:

  1. m. Éxito, resultado, término de un negocio.