The author recommends reading Blood and Ash together with its Flesh and Fire companion prequel in release order. Her current guidance runs through The Primal of Blood and Bone; A Crown of Ruin then bridges Primal and the announced final Blood and Ash novel, The Throne of Bone and Ash.
The combined order interleaves Blood and Ash novels with Flesh and Fire companion-prequel novels, then distinguishes an optional compendium, a bridge novella and an announced final novel. Shelf of Worlds keeps those roles explicit so optional or bridge material is not mistaken for a numbered series installment.
Sources: Jennifer L. Armentrout — official FAQ and combined reading order, Jennifer L. Armentrout — Visions of Flesh and Blood, Jennifer L. Armentrout — A Crown of Ruin
Concludes Flesh and Fire and follows the optional compendium position in the combined sequence.
Optional bridge novella placed by the author between The Primal of Blood and Bone and the final Blood and Ash novel.source
Short answers, with sources.
Yes for the recommended first-read path. Jennifer L. Armentrout says Flesh and Fire is a companion prequel rather than a fully separate prequel, and that the two series are meant to be read together in release order for maximum enjoyment.
Sources: Jennifer L. Armentrout — official FAQ and combined reading order
You can, but we do not recommend it for a first read. Armentrout warns that explanations in Flesh and Fire can spoil mysteries in Blood and Ash when the books are read out of the intended combined order.
Sources: Jennifer L. Armentrout — official FAQ and combined reading order
No. Armentrout calls Visions a world compendium and says it does not need to be read as part of the series. If you include it, read it after A Fire in the Flesh.
Sources: Jennifer L. Armentrout — official FAQ and combined reading order, Jennifer L. Armentrout — Visions of Flesh and Blood
Read A Crown of Ruin after The Primal of Blood and Bone and before The Throne of Bone and Ash. Armentrout describes it as a free bridge novella covering the unseen aftermath between those two books.
No. The current official material still points forward to The Throne of Bone and Ash as Poppy and Cas’s final Blood and Ash book. Shelf of Worlds does not assert a release date until one is directly verified.
These sources support the reading order and important details about the books and their editions.