Mohan's Book Exchange

Customers post the books they want to sell, Mohan writes and checks every listing, and shoppers browse and ring each other directly.

Who this is for

Mohan Kulkarni runs Vidya Book Depot, eleven feet wide, on a lane behind Dharampeth in Nagpur. Second-hand school books on the lower shelves, Marathi novels above. About forty regulars, no staff. Every second day someone walks in with a jute bag of old books and asks him to buy them. He has no room and no cash to spare, but he knows three people who would want that Wren and Martin, and he cannot hold all of it in his head.

How the job is done today

There is a spiral notebook near the till where Mohan writes: Sunita madam, Std 9 science guide, 150, called Tuesday. Half the entries are stale by the time he reads them again. He also has a WhatsApp group with about ninety customers where people send blurry photos of book piles, and by evening those photos have scrolled past six forwards and a wedding invitation. So people ring him instead. He answers the same question eleven times a day, is that dictionary still there, and he is usually not sure.

The screens, in order

1. Browse books — Lets anyone who opens the app see what is on offer right now, newest first, in large dark text on plain white.
2. One book — Shows the full details of a single book and the seller's phone number, so the buyer can ring them and fix a time.
3. Post a book — Lets a seller type the book name, the writer and their asking price in three boxes and nothing more.
4. Mohan's checking list — Puts every newly written listing in front of Mohan so he can correct the wording or the price and let it go out, or drop it.
5. My books — Shows a seller what they have posted and lets them mark a book as gone once it is sold.

What it keeps track of

• Books on offer — book name, writer, what the seller wants for it, school book or general reading, condition in one line, still available or gone
• Sellers — name, phone number, which area of the city, what they have posted so far
• Waiting for Mohan — which book, what the assistant wrote, what Mohan changed it to, passed or dropped, when

The one decision that matters

Does the browse page lead with photographs of the books or with words. Photographs are the obvious choice for anything being sold second-hand, but these photos get taken inside a dim shop on old phones, they come out yellow and tilted, they take time to load on a slow connection, and outside in the afternoon a small cover picture is a grey smudge. Words win here. Book name in large dark type on a white background, writer under it, price at the end of the line, nothing else. A woman standing at a bus stop should be able to read four listings without shading her screen with her hand. Photos can be added later, small and optional, once she has already decided to open the listing.

What to leave out of the first version

No payments and no chat inside the app. Money between two people who both live in Nagpur is settled at the shop counter or over UPI on their own phones, and the moment the app touches the money Mohan becomes responsible for a book that never arrived. Also leave out ratings and seller history. With forty regulars, reputation is already a real thing in the lane, and a one-star review on a stranger's name would only bring Mohan a fight he did not sign up for.

How you would know it worked

A man Mohan has never seen before walks in at eleven in the morning, holds his phone up and says, this Std 10 algebra book, the person says he stays in Manish Nagar, can I meet him here. Mohan did not put that customer in touch. The app did.

Build it

Paste this in and let it run.

I run a small second-hand bookshop in Nagpur and people keep bringing me books I have no room to buy. Build me a phone app where a customer types the book name, the writer and what they want for it, and something writes a proper short listing out of that and sends it to me first, so I can fix the wording or the price before anyone else sees it. Once I pass it, it should appear on a page anyone can open, newest at the top, with the book name in big dark letters on white, because my customers read this standing on the road in the afternoon sun on old phones. Let them search by book name and filter school books separately from novels. Show the seller's phone number on the listing itself so the two of them ring each other and settle it. I do not want to handle any money.