To be totally honest, I wasn't expecting to enjoy these books as much as I did. I guess I just wasn't sure WHY I was reading these ones, if that makes sense. The Hiden light novels felt like they had more of a purpose. (At least at the time I was reading them, they hadn't been animated yet.) Those ones took place in the future from the series, gave us a sense of what happened between the time of Naruto's end and Boruto's beginning. The Shinden novels (the first two, anyway) are different.
We already saw Itachi's story. Well, I'm sure a lot of people
considered it filler, but I really liked that little episode arc, showing Itachi's childhood, giving us a little more insight into all that he went through in his quest for true peace... At least, I thought they had been insightful until I read the books. And now I'm glad I did. I only realized once reading the books that I hadn't truly understood Itachi's thoughts before now. I saw his actions but could only guess at his mindset. If nothing else, the Shinden novels gave me some insight into exactly how Itachi viewed his place in the ninja world and his relationship with his brother. It kind of made me realize that-- good or bad-- we've only ever seen Itachi through Sasuke's eyes, not his own.
In general, I felt a lot of it was just written very well. Takashi Yano is the one who wrote Shikamaru's light novel, too, and I remember feeling that one had a really firm grasp on the characters-- something not entirely true about Kakashi or Sakura's light novels. And I feel like here he did a really good job in explaining some of the little things. Like his relationship (or lacktherof) with his classmates who he was incredibly distant from. Once it was revealed that Itachi was actually one of the good guys and incredibly kind, I think that affected how I viewed his treatment of everyone else. But in truth, he was very... brusque with everyone around him. Cold, even if it wasn't intentional. He was just too focused on his own success as a ninja to focus on his interpersonal skills.
The second one, in particular, had more of a focus on his relationship with his father, and where that rift came from and how grew until they barely knew each other. As well as just giving a little more insight into how Danzo ran things. (As if we needed another reason to hate Danzo.) But I was particularly interested to hear that he was the one who leaked the info that Naruto was the Nine Tails jinchuriki to the general public. And it was interesting to consider that his reasons for killing Shisui may not have been entirely greed-motivated. Shisui had plans to incapacitate Fugaku in his efforts to stop the coup. (Speaking of, I was particularly fond of the imagery Yano drew for us-- of Itachi and Shisui standing side by side, arms out, trying to hold back the tide of their entire clan's anger.) And I was forced to admit that there is some sense in Danzo's reasoning-- that in any cause, "the head can always be replaced."
And, lastly, I think it was important to read these light novels to really see the prejudice between the village and the Uchiha clan. I remember, at the very end of the manga, it came up in Sasuke's thoughts that he'd been ostracized because of it, but that didn't really feel true... If anything, the fallout from the Fox attack was after his time. Itachi was 'bullied' for it, to an extent, but I never felt like Naruto and Sasuke's classmates ever really understood it well enough to know why the Uchiha clan might be blamed for it. In general, I just felt like the Shinden light novels filled in some holes.
...ON ANOTHER NOTE...
It's almost hard for me to consider this last book part of the same series. I definitely would have been fine with book three continuing to follow Itachi throughout his time in the Akatsuki... but when all is said and done, this is a fitting ending. I am glad that the focus switched to Sasuke, given that his future was Itachi's focus for most of his life.
I was kind of disappointed to see that the author changed... I've gotten a little attached to Takashi Yano's writing style. There just seem to be fewer mistakes throughout the novels he wrote... fewer instances where the wording was just awkward or the characters' names got mixed up. This last book was subject to some of those moments and errors, but it was pretty good overall. (It was noted that Shin Towada wrote the Akatsuki Hiden novel as well, but as that one has yet to be translated into English... One book feels a little too early to say anything definitive about his writing style overall.) There were some really well-worded passages, and I think this book did a good job of giving us a better explanation of what exactly Sasuke is doing in his 'journey to atone for his sins'. Though the idea that he might just be traveling the world, righting wrongs wherever he sees them, is such a main protagonist sort of quest... that it just feels kind of funny to me. Though I did really like the little scene with his old team mates, where Jugo explains that one possible reason for him to never settle down permanently in the village is that he doesn't want to attract danger there, in the form of evildoers seeking revenge against or just targeting him.
I will say that the particular short story around which they chose to write this explanation of Sasuke's journey felt a little... eh. Like, just another short story someone came up with for fun. So I don't think the events of the plot itself will leave any long-lasting impression on me. But overall, I did really like the three Shinden novels. I think it did some things very well, giving us some further insight into the Uchiha brothers' mindsets that, honestly, were more than I was expecting from them.