Bragelonne is very hit and miss. It's like a Dumas Musketeer novel hidden within a Maquet historical novel. It's not always cohesive and toward the end threatened to fall apart. The musketeer story makes up about the last third of the novel alone, the rest is concerned a lot with a chronicle of the early ruling years of Louis XIV, before out of the blue the tone shifts completely, with the "man in the iron mask" conspiracy, which goes back more to the style of the first books.

It's Dumas' novel that owe the most to Maquet, who wrote many chapters that, very unusually, Dumas barely revised (he didn't have time). The book got longer and longer, with Dumas' lesser involvement Maquet almost lost control and as the book got much longer than what they were paid to write, Dumas lost interest and left most of the ending to Maquet. It's still readable for all that, with some patience, and it's nice to see where the characters are going (and where they end, as only one survives beyond the book). Bertière's book might encourage you to read it, even if she's fairly critical of it.

Her biography of Mazarin would make a nice companion to Vingt Ans Après. Her vision of the man is radically different from Dumas's buffoonesque character, but her portrait is almost as colourful.