On the positive side: the pages turn themselves and it will only take a day and a half or so to read.
On the negative side: it is an appallingly researched book full of errors, historical, scribal and geographical.
This book is 280 pages long, all in. That sounds like quite a lot for Aethelflaed, to whom the primary sources have not been kind. However, when you take out the end notes, glossary, index and bibliography, this comes down to 232 pages. 216 when her place in history is deducted, 206 when Aelfwynn's chapter goes west and when you take out the chapters on Alfred, Aethelwold, Aethelraed, etc, this becomes more like 70 pages – which she shares with Edward the Elder. And even this isn't as generous as it might seem.
Arman uses a lot of Irish annals as sources and these were written much later and contain quite a lot of questionable information, beyond bees and ale. She also makes use of works of fiction, refuting some of the more lively inventions, such as tales of Aethelred's unpleasantness as recounted by Bernard Cornwell and friendship between Aethelflaed and Aethelwold, but this really has no place in a history book. Plus there is a lot of stuff that is speculative at best, such as scouting the idea that she may or may not have received training in weapons, with an account of some other noble women who may (or may not) have led armies. This felt like padding.
The writing style is casual, which can work well, but in places this makes it very hard to take seriously, such as when it comes out with pearls such as 'the Mercians were a proud people'. It doesn't appear as if this book was edited beyond someone clicking spellcheck, as you have deducted instead of deduced (plus a few other examples of this) and 4-5 occasions were a sentence makes no grammatical sense, because it appears as if Arman started saying something, went to make a cup of tea and then came back and concluded the sentence in a way that makes a nonsense of its opening. I don't believe it was given the once over before it was published, as Alfred and Aethelraed campaigning in 992-6 instead of 892-6 would surely have been picked up as a mistype. Alfred must have been great indeed if he was still fighting almost a hundred years after he died.
Here's an incomplete list of errors:
Calls Mercians and Northumbrians Saxons.
Lindisfarne raided in 793 and 'there may have been more before' – yes there was, we know there was. It's in The Chronicle and gets mentioned in most books.
States that Alfred had 4,000 men at Edington and outnumbered Guthrum – I'd like to know how she knows that.
She claims Aethelstan's mother is unknown – she isn't. It was Ecgwynn.
Aethelwold, cousin of Edward the Elder, was the first Christian king of Northumbria 'in nearly a century'. Yikes. If there's one things the Northumbrians weren't short of in the 9th century, it was Christian kings.
Ealswith, married the 'second son of the King of Wessex'. No.
Offa's wife, Cynethryth, holding power during the minority of her son. What minority?
Others:
The idea that the Witan chose the king. I can believe it was necessary for an atheling to gain the acceptance of the political nation, but the way she describes it, she gives a far more active roll to the Witan in king making.
Arman has a very shaky understanding of the Burghal Hidage in relation to the manning of the walls. She doesn't seem to know that it was worked out by poles and this equated to the number of hides that theoretically supported the burh. She sees the Burghal Hidage as listing 'the number of hides they (the towns) contained' and sees the walls of Stafford spanning 1200 metres and being equivalent to the measurement of 960 hides, which I think she believes is the area contained within, although in fairness that section on Stafford is ambiguously worded.
She describes Aethelflaed's conquest of Derby in 917, but doesn't mention the context of Edward the Elder defeating three separate Viking armies that year and him drawing off most of their strength, which arguably made her conquest feasible.
Arman recounts the idea of Paul Hill's that Alfred was either deposed by his nobles or was going to be deposed by his nobles at Chippenham. However, there is no evidence of this. Alfred's position subsequent to Chippenham was that he still had enough support to call out the Fyrds of Somerset, Dorset, Hampshire and parts of Wiltshire, ie everywhere practicable, which seems unlikely if he had been deposed. The ealdormen who did vanish from the witness lists could easily have fallen at Edington, only Wulfhere is labelled as having deserted the king.
There are also some basic errors of geography. Gloucestershire is NOT flanked to the west by Berkshire, it's not even on any flank. Bakewell is NOT south of Nottingham and I'd love to know in which universe Haesten's army in Powys could be said to be 'perilously' close to the Viking army in Exeter.