The first half of the book is entirely about Richard attempting to evade capture while making his way home from the crusades, and his imprisonment by the Duke of Austria and the Holy Roman Emperor. While that does make a significant portion of it a little bit lacking in action and adventure such as we saw in the prequel Lionheart, it does make for a highly political novel as Richard and his allies maneuver for his release. It's also a personal journey of self discovery for Richard as he copes with his imprisonment and gets to know his captors. It heavily involved Holy Roman Emperor, Henry VI.
The second half of the book is about Richard attempting to politically and militarily regain what he lost during his time in the Holy Lands and captivity, so there's more action again in the second half.
As ever with Penman, the story is told from multiple points of view with characters that are well fleshed out with complex relationships among each other, making it a multidimensional and highly enjoyable novel, even if it does take a while to get through, being somewhat long.