These are what we call the 'YMMV items.' Things that some people find in this work. We call them 'your mileage might vary' because not everyone sees these things in the same way. This starts discussions in the trope lists, a thing we don't want. Please use the discussion page if you'd like to discuss any of these items.
YMMV: Septimus Heap
Angst? What Angst?: Septimus seems pretty unconcerned for the disappearance of Nicko in Physik.
Awesome Art: Mark Zug's drawing s of the characters and settings in the books.
Canon Fodder: Numerous details, places and people across the series.
Complete Monster: Queen Etheldredda the Awful. It is strongly implied that she drowned her children (except Esmeralda, who escaped, and Marcellus, who was needed to make the Immortality potion) so that she could be Queen forever.
Continuity Lock-Out: If you haven't read Magyk before Flyte or Physik before Queste, you won't understand much of the plot.
Ending Fatigue: The books have an habit of lasting long and even after the climax, there is usually still a bit of plot before the end.
Fan Preferred Couple: Septimus/Jenna and Marcia/Silas in spite of the fact that Septimus and Jenna are siblings and that Silas is married and has seven kids.
Harsher in Hindsight: The events leading up to the outbreak of the Darke Domaine in Darke bear an uncanny similarity to the Fukushima accident, namely the safety lapses in both cases.
Played With in Darke. Sure, it was Merrin Meredith who unleashed the Darke Domaine, but it probably wouldn't have happened without Septimus's and Marcia's poorsafety policy.
The escalation of the crisis was also hardly the paramount of good decision-making.
Informed Wrongness: Jenna is a MacGuffin Girl and is told to go away in Syren rather than get into danger, notwithstanding the fact that she isn't one outside of the Castle.
It Gets Better: A few people complained about the lenght of Queste's introduction, specifically the Merrin Meredith scenes.
Magnificent Bastard: Tertius Fume. Between dragging Alther into the Darke Halls when he's Banished, sending Septimus on the Queste with a rigged Draw, he's definitively a magnificent antagonist, especially compared to his rather dull predecessors.
The Two-Faced ring, and the way you get it off. You have to take it off the Other way, i.e you have to cut the finger off it was on.
The Hunter. Going around and killing people like animals. It's even called "hunting". His relentless efficiency mode.
The illustration of a Thing in Darke.
Some milder examples: Septimus's appearance Darke and Jenna's witchy clothing in Darke; DomDaniel melting down to a pool of slime in Flyte; Merrin Meredith being Consumed by DomDaniel in Magyk.
Nightmare Retardant: The Things' faces, as shown in Darke, look almost weird, rather than scary.
The Woobie: Sarah Heap. Between losing Septimus, Simon and Nicko at various times and rarely seeing any of them, there is not much happiness in her life.
Marcia puts up Jenna for the Heaps to adopt in Magyk despite different eyecolours and Magykal powers making them a rather poor hiding place for the princess.
What did you intend when running back into the Palace when the Darke Domaine was spreading out, Sarah?
