This is an awesome discussion.  It's definitely something I've considered.  

I am definitely making some characters older or younger to fit them all in a specific window of time.  I didn't bend more than five years.  My book is about the Harlem Renaissance which is debatable when it started.  Some historians say the window was about twelve years, while others argue almost forty years.

I am keeping all major historical events in tact.  With that being said, there will be a disclosure about how all characters and events are used for entertainment.  

I wouldn't move a war, nor would I change the facts of a war.  However, I would pull people from different points in the Renaissance all to the same window, while keeping all of their career achievements in tack and factual chronological order.  Which doesn't throw the story out of whack because its not a decade difference and they did eventually all meet in real life. Not to mention, the attitudes and social norms are the same for all the time I'm' bending.

I do think content is more important than being factually sound. 

I think it really depends on the detail that is bending. If the bending detail could be mistaken for just sloppy writing then it is a deal breaker. Also, common know events or places should not be moved or changed for convenience. However, there are a lot of untold stories in history. We can not be sure about everything and so I think we can assume that we will never know the absolute truth when it comes to much of history. Also, if the writer provides a reasonable explanation for the discrepancy there is more room for bending.

It can be difficult writing an accurate historical (fictional) book but I think it can be done. Clan of the Cave Bear is a good example but there are also some historical romance books that I found great fun to read like Sweet Savage Love by Rosemary Rogers. It's an oldy but it's set in some very interesting times and I thought it appeared quite accurate (of course it's been a long time since I read it so ...). The Far Pavilions and Trade Winds are two other books that come to mind (MM Kay) which both handled the issue of character within the historical novel brilliantly, imo.

Perhaps the question to ask: to what end are you reading historical fiction? On one end of the spectrum, I'll propose that it's to read a great story, period. On the other end, let's say the aim is to learn about history in an immediate manner. On the story end of the continuum, it's likely historical accuracy must be sacrificed to generate story power. On the other end, the opposite effect is most likely the case.

As such, those reading a novel for purposes of learning history will revile books written with the license allowed at the other end. Those reading for pleasure will be (perhaps) vaguely disappointed by a book written within the strictures of rigid historical accuracy. Is it possible to please both crowds? Maybe - and it could be that the odds improve the less is known about the period. But then other dangers lurk - if little is known about the period, is it of interest?

One successful answer: The Clan of the Cave Bear, and all that followed.

Bit of a broad brush there, Sophie. Personally, I think story trumps all - if it's engaging enough, I don't care and I don't go look up the real history to check facts. To take an example from another genre, I suppose many rushed to evaluate the efficacy of Brown's The Da Vinci Code. I couldn't have cared less. I imagine he was pretty accurate, but I didn't read it to learn about Catholic history.

Very well said, and agreed. Unfortunately, I think there's also a tough line to walk with anointing people with 20th/21st century sensibilities, as you put it. Characters who think realistically for their era are often completely unlikeable in our era, and a lot of readers will be turned off to the book because they simply can't relate. On the other hand, adjusting an historical mindset to match our own just comes out lame. It's hard to find common ground with someone who lived centuries ago, but I think the key is finding that common ground.

Touche!

I think it depends on how much and what kind of bending you do. For example, you can't have someone driving a car in 1825 or wearing a bustle in 1540. But you can make up conversations or have your fictional character participate in a real event. And if you do mess with history, you should tell you reader, imo. For example, in my my historical novel I have one of my characters interact with Bat Masterson, but I also have notes at the end that let readers know that my research found no women associated with the man during his time in Tombstone as well as the fact that I moved an actual train robbery to a later date.