my take: i heard several reviews on NPR ... none of them positive. hubby included this in the 12 days of Christmas pile, so i kind of had to read it even though i was leery. it was a pleasant surprise to very much enjoy the lacuna.
that said, it took me a long time to read - it's got lots of pages and it was slow going. only a minus for someone who needs to read lots of books to, say, review on a blog. be warned, but don't be dissuaded from reading this.
as a fan of most things art history, i grooved on the plot including diego rivera & frida kahlo. it was great to get some mexican & russian political history in, as well. the book covers a vast scope of history, and i think barbara maybe over-reached there. but very well-written.
my source: 12 books for 12 days
my verdict: historical/political fiction almost at its best. worth a read, may take a while.