The book is the Good Housekeeping Cookery Book and it was first published in 1925. Here is the recipe copied exactly as written. I like the old fashioned sounding instructions.
Strawberry Jam with LemonProportions.-- To 3lb. strawberries allow the juice of 1 lemon and 2 1/4lb. sugar.
The small or medium-sized red strawberries are the best for preserving. Pick the fruit and carefully reject any that is unsound. Put it into the preserving pan and bring it to the boil stirring all the time. Meanwhile have the sugar weighed out, crushed if necessary, and made very hot in the oven. Add it gradually to the fruit without letting it go off the boil. Pour in the strained lemon juice, and boil together until the jam will stiffen.
I particularly like the phrase " boil together until the jam will stiffen" because without adding pectin strawberry jam can take an age to boil to setting point. Mine has set though it could be described as a "soft set", still yummy though.
I used to seal my jam jars with wax paper circles and the cellophane secured with elastic bands but I have now found that providing the lids are in good condition then the jars can be sealed with the lids alone. If the hot glass jars are filled with the hot jam and the lids which have had boiling water poured on them are screwed on immediately then the cooling jam pulls a vacuum and seals the jar. I've used this method for several years now and have only had a couple of failures so some of the jars have been used for several years and they still seal. You can be sure that the jar has sealed securely if the lid becomes depressed in the middle after cooling. Any jars that don't do this we use straight away.