While authors prefer their books to be ordered through your local bookstores (they're good to us), if that is inconvenient, you can get them via the internet.  Amazon & Barnes and Noble carry most of my books.  Both offer venues carrying out-of-print books.

Schools, Libraries, Museums, etc. - Order info here. Most are available at a good discount.
Book Order Page
Children's Books written and illustrated by JH:

Box Turtle (Globe Pequot 2018)
Floaty (Holt - 2017)
Bunjitsu Bunny Vs Bunjitsu Bunny (Holt - Fall 2017)
There's a Bug on my Book! (Dawn - 2017)
Bunjitsu Bunny Jumps to the Moon! (Holt - 2016)
The Cow Said Meow (Holt - 2016)
Bunjitsu Bunny's Best Move (Holt - 15)
Noisy Bird Sing-Along (Dawn - 14)
Tales of Bunjitsu Bunny (Holt - 14)
Noisy Frog Sing-Along (Dawn - 13)
Basic Guide to Frogs, Snakes, Bugs, and Slugs (Falcon - '13)
Duck to the Rescue (Holt - 13)
Katie and the Puppy Next Door (Holt - '13)
Noisy Bug Sing-Along (Dawn - '13)
Cows to the Rescue! (Holt - '11)
Ten Little Hotdogs (Marshall Cavendish - Fall '10)
Pigs To The Rescue! (Holt - Spring '10)
Who's at the Seashore? - Northword - 2009
A Daddy Longlegs Isn't a Spider (Finney/Windward - Fall '09)
Katie Loves the Kittens - Henry Holt - 2008
Chickens to the Rescue - Henry Holt - 2006
Tudley Didn't Know  Sylvan Dell - 2006
Mouse in a Meadow   Charlesbridge - 2005
Frog in a Bog   Charlesbridge - 2004
Pipaluk and the Whales-  National Geographic - 2002

From the "Nature Upclose" series (Children's Press/Scholastic):
A Mouse's Life - 2001
A Mealworm's Life - 2001
An Earthworm's Life - 2000
A Hummingbird's Life - 2000
A House Spider's Life - 2000
A Pillbug's Life (Year 2000 CBC Outstanding Children's Science Trade Book) - 2000
A Monarch Butterfly's Life - 2000
A Ladybugs's Life - Children's Press (Starred Review Science Books Bulletin) 1998
A Salamander's Life - 1998
A Luna Moth's Life - 1998
A Slug's Life - 1998
A Wood Frog's Life - 1998
A Dandelion's Life - 1998

The Animal Rescue Club - Harper Collins 1998
Honest Tulio - Troll 1997
The Ups & Downs of Simpson Snail - Dutton  1997
Simpson Snail Sings - Dutton  1996
J.J. Vs. the Babysitter - Troll  1996
Lights Out! - Troll  1995
I'm Not Scared! - Scholastic  1994
Wanted: Perfect Parents - Troll  1993
A Guest is a Guest - Dutton  1991
The Clover County Carrot Contest - Silver Burdette 1991
The Super Camper Caper - Silver Burdette  1991
The Great Leaf Blastoff - Silver Burdette 1990
The Day Off Machine - Silver Burdette 1990
Montigue on the High Seas - Viking Penguin (Book of the Month) 1990
Ibis, a True Whale Story - Scholastic (ABC AWARD, NYT Pick of the List) 1990
Ellen and the Goldfish - Harper 1990
Amanda and the Magic Garden - Viking Penguin  1987 
The Talking Tree or Don't Believe Everything You Hear - Vik/Pen - 1986
 Amanda and the Witch Switch - Viking Penguin (JLG Selection) 1985
Talester the Lizard - Dial (JLG Selection) 1982

Children's Books illustrated by JH:

Wait Till It Gets Dark - Globe Pequot 2017
Mort the Sport - Orchard 2000 (Top 10 Children's Sports Books 2000)
Sound the Shofar - Harper Collins 1998
Hooray it's Passover! - Harper Collins1996
Young Thomas Edison - Troll 1995
The Story of Myrtle Marie - Harcourt Brace  1995
Let's Count! (Pop-up) - Joshua Morris  1995
The Fisherman & the Turtle Princess  - H.B 1994
Buzby, to the Rescue - Harper Collins  1993
Hannukah Nights, Hannukah Lights - Harper Collins 1992
Buzby - Harper Collins  1992
Young Christopher Columbus - Troll 1992
Young George Washington - Troll  1992
Rainboots for Breakfast - Silver Burdette 1989
Shopping for Snowflakes - Silver Burdette 1989
Charlotte Shakespeare & Annie the Great - Harper Collins  1989
Charlotte the Starlet - Harper Collins  1988
Go to Sleep,Nicholas Joe - Harper Collins 1988
Snuggle Piggy and the Magic Blanket - Dutton  1987
Charlotte Cheetham, Master of Disater - Harper Collins  1985 

Children's Books written by JH:

Sarah and the Terns - Random House  1997
Ben's Birthday Wish - Random House  1997

Adult Non-fiction
Cricket Radio: Tuning in the Nightsinging Insects (Harvard - '11)
Field Guide to Night-singing Insects of the NE - Stackpole Bks - 2009
Discovering Amphibians, Frogs and Salamanders of the Northeast - Downeast Books - 2006
Discovering Moths, Nighttime Jewels in Your Own Backyard - Downeast Books - 2003

Animated Video: 

The Fisherman & the Turtle Princess - ALC Press 1994