Age appropriate longer books for 5 year old fluent reader

Mine likes The Dragonsitters Detective books
Geronimo Stilton books
The Faraway Tree
Mr Majeica

Jack hazard
Flat Stanley
Worst witch
Allen ahlberg novels
Dogman
Shorter versions of the classics - maybe he was slightly older but Gillian Cross Version of the Iliad and Odyssey my older DS read about 50 times!
Horrible history books - my older Ds was obsessed with these
Both my DS loved Asterix from about 5 though heaven knows what they took from the puns!
I gave my older ds Harry Potter at the end of reception and although he read it to himself fine, I felt like emotionally it tuned much more aged 7ish, all that stuff about schools, friendships, the jokes were better suited to a bit older.

It’s hard to get the balance right when they love books but are still little

Daisy and the trouble with..... Don't let the fact the main character is female put you off ds loved these.
Flat Stanley my reluctant reader son couldn't put these down.
The simple Roald Dahl books eg Esio trot.
Captain underpants.

The Claude series is lovely for a readIng 5yo

The owl who was afraid of the dark and all the other Jill Tomlinson books

Oliver Moon series

The younger Roald Dahl - the enormous crocodile, the giraffe the pelly and me etc

Zoe’s rescue books series by Amelia Cobb

My nearly 6yo has been a fluent reader for quite a while. Dick King Smith has been a winner as well as some Judy Blume books like Freckle Juice.

We did how to train your dragon too, just know that the last books in the series are a lot more grown up (there's a big war). Don't give the full set at once, as we did. They are great, nothing like the lame movies!

Enid blyton.

Can’t stand horrid Henry.

My DS started on the How to Train your Dragon series at that age. There are 10/11/12? of them now (they were a fairly new series when DS was small) and well worth it. They are INFINITELY better than the films, and in addition to reading the books, the audio books are fantastic. David Tennant reads them (not sure how far into the series he does but certainly the first 5/6 I think) and they kept our entire family entertained on long car journeys many times over the years when DC were younger.

At that age my ds loved the Dogman series of books.

Time Hunters series by Chtis Blake. My boys were 5/6 when they read those and loved the travelling through time aspect and visiting different cultures. Very fun.

The Frogspell series. Cant remembered the author. Funny magic themed stories with good villains for that age.

Try Zoey and Sassafras series.
My dd is a fluent reader aged 5 but also loves nature and science so we get her the National geographic readers.

In addition to the above...
Rabbit and Bear
Agent Weasel
Mr Penguin

DS at 5 isn't that good a reader yet but is loving having the Magic Treehouse series books read to him. Of the chapter books I read to him they are the first ones I think he'll be able to read himself. They are short chapter books which still have quite a few pictures, but there are loads in the series - they are adventure with a bit of non fiction and the plot continues across books. Our library has both the American original versions and the British English versions which have different titles (Wikipedia has a list of which is which).

We have the Ottoline books and he loves them but the language is a bit more complicated and the plot is slightly more complex (a bit more is between the lines rather than stated) so I think he is further from being able to read those independently.

We've also had a couple from the Oliver Moon series out from the library, which he's enjoyed. They are adventure stories about a young wizard. They are a little bit longer than the Magic Treehouse books but I'd say just as accessible in terms of language / plot.

aquintillionwords.com/2020/10/04/the-snark-book-review/

The Snark by Justin Davis! This is fantastic, I managed to read a preview! Its not too long,great illustrations and funny too!

My DS preferred the Dirty Berty books to Horrid Henry.

Beast Quest were very popular when he was that age, but that was 15 years ago.

Percy Jackson
Artemis Fowl

Daisy and the trouble with... books by Kes Gray are brilliantly funny.

Roald Dalh, my five year old has nearly finished Matilda, there are quite a few tricky words but he asks one of us what they mean when he gets stuck.

Mallory towers, horrid henry, the first harry potter is quite accessible.

Lots of boys enjoy Malory Towers.
My Naughty Little Sister is great for early readers.
I would say Captain Underpants is too old for a 5yo.
Dixie O'Day series is good.
Jolly Rogers Series
Ottiline series
Horrid Henry

Dick King-Smith
Roald Dahl has some pretty complex vocabulary, from having been in this position!

Horrid Henry - some of them are specifically aimed at early readers
Captain Underpants
Roald Dahl - the easiest ones are The Enormous Crocodile, Esio Trot and The Giraffe, the Pelly and Me