Tessera can bind your letters into a book

Picture eighteen birthday letters to a kid, sealed one a year, then opened all at once when they turn eighteen. Or twenty-five anniversaries. You wrote them alone, across a decade or two, and each one arrived as its own little folder of files. The day someone finally gets to read them, what should they hold? A zip on a drive is the wrong ending for that. A book is the right one.

So Tessera can now bind a run of letters into a real booklet you print, fold, and sew at home: an actual gathering of paper you stitch down the spine. (If you’re new here, a letter with no moving parts covers why Tessera treats paper as the reference copy in the first place.)

What the composer builds

You hand it a series and it orders the letters by date, then assembles a volume. There’s a title page that reads “Letters to ___, 2026–2044” with the real span filled in. Each letter becomes a section with its dates written out in words, not digits, because a book of this weight shouldn’t say “05/2031.” The broken-token art from every letter in the series gets gathered onto one leaf, a plates page, so the halves you kept and the halves that travelled sit together for the first time. Then a colophon at the back saying what this is and how it was made.

The part that took the real work

The hard problem is imposition. On a folded booklet, the pages don’t print in reading order. Fold one sheet in half and it holds four pages: the outside is page one and the last page, the inside is two and the second-to-last. Scale that up to a stack and the sequence gets genuinely knotted. You have to reorder every page so that after you print double-sided, fold the whole thing in half, and sew it, the reader turns from one page to the next and it just runs forward.

That reordering is pure arithmetic, and I tested it as arithmetic. js/booklet.js does the imposition; tools/test-booklet.js runs it against 8, 16, and 24-page fixtures and checks every page lands where it belongs. But arithmetic passing isn’t the test that counts. I printed the 8-page fixture, folded it, and turned the pages by hand. That’s the only proof I trust, because a home printer is where clean math goes to meet reality.

Built for a bad printer

The whole thing assumes you own a cheap inkjet and nothing else. Duplex printing on those drifts, so the layout tolerates about 3mm of front-to-back misalignment before anything important gets clipped. The rules and guides are ink-light. And there’s a firm ceiling of five sheets per signature: past that, folded paper fights back and the inner pages creep out of the trim, so Tessera stops you and says take this one to a print shop.

Two ways to bind, depending on your patience. Fold and sew, which is a pamphlet stitch for a single signature and a kettle stitch once you have several. Or cut and staple, if thread isn’t your thing. Either way the last page that prints is the binding instructions, the words and one diagram, so the sheet in your hand already knows what to become. You print the book and the manual falls out of the same stack.