First off, you might want to double-check that full title because the one I know is 'Blood Bride' and a separate work called 'The Lament of the Werewolf' – maybe you've got them mashed together? If it's 'Blood Bride' I'm thinking of, the one by Joey W. Hill or a similar paranormal romance, it's about a human woman, often named Sela, who gets tied up in vampire politics and ends up bound to a powerful vampire lord, sometimes as part of a treaty or to stop a war. There's usually a ton of tension between duty and actual desire, and the 'blood bride' concept means her life is completely intertwined with his. I found the political maneuvering more interesting than the romance, honestly; some of the side characters plotting in the court scenes were the best parts. If we're talking about a werewolf story, the plot gets totally different – a 'lament' suggests a tragic backstory, maybe a werewolf cursed to lose his mate, so I'm leaning toward this being two separate books someone's asking about as one.
If it's a specific web novel or serialized fiction, the plot could involve a human bride sacrificed to a werewolf alpha to appease him, and her discovering his tragic past and the real curse he's under. That 'lament' in the title hints at a mournful, poetic tone, maybe from his perspective about losing his humanity or a past love. The bride might be the key to breaking his curse, but it's not a smooth process – lots of angst, mistrust, and dark forest atmosphere. I'd need more specifics to nail it down, but that's the general shape of stories with those kinds of title keywords.