Of the remaining three reveals, one was entirely tangential and inconsequential to the story, completely untelegraphed, happens around the 98% mark, and left me with a “Huh. Well… that’s nice, I suppose.” reaction.
closed as off-topic by Hot Licks, Edwin Ashworth, Bread, Janus Bahs Jacquet, Nigel J Apr 29 '18 at 15:06
This question appears to be off-topic. The users who voted to close gave this specific reason:
- "Please include the research you’ve done, or consider if your question suits our English Language Learners site better. Questions that can be answered using commonly-available references are off-topic." – Hot Licks, Bread, Janus Bahs Jacquet, Nigel J
I'd suggest untelegraphed here means that the subject reveal was not given away before the reveal. Merriam-Webster provides this definition of the transitive verb telegraph:"to make known by signs especially unknowingly and in advance." (https://www.merriam-webster.com/dictionary/telegraphed).
The phrase 98% mark indicates that the reveal happened 98% of the way through the story, perhaps.
The review is very condensed. 90% and 98% describe the position in the book as an alternative to page numbers.
'Untelegraphed' is related to the meaning  in Merriam-Webster, already cited. It is clear 'mattgemmell' is describing a fault in the writing from an author's point of view. In this case it is a failure to set the scene; a failure to create a believable setting for the reveal; and his failure to give any hints about this character/ happening. 'The third reveal,' cheats the reader. Dan Brown likes magic; but no-one would take him seriously if a boy wizard popped up, totally untelegraphed, and sorted everything. This reviewer thinks the reveal is the wrong sort of surprise.