Let me start by saying I love your books, and I've read a lot of travel guides over the last 35 years of my international travels. But I have to say that your advice on buying advance French rail tickets from home (I live in California) via the en.voyages-sncf.com/en web site was a bit off the mark. For those looking for a good alternative, I suggest this one instead:
The SNCF site initially presented itself to me as being "foreigner friendly". It has one of those Union Jack buttons in the upper right corner to translate to it English and during purchase I could select that prices be displayed in US dollars. But as I proceeded through the purchase, I found it got harder and harder to use.
First, it forced me to enter a French cell phone number as part of identifying myself. I couldn't leave the field blank and it wouldn't accept my US cell number. So I made up a French looking number to get past it. If SNCF is going to try to send me a text, I'm not going to get it.
Second, it wouldn't accept payment on my US credit union VISA card. Even after I called the credit union to tell them to let the purchase through, SNCF wouldn't accept the card. I was able to pay using a US credit union Mastercard, after I called the credit union to preauthorize the purchase. But both required phone calls to the credit union. I spent hours on the phone puzzling through this.
But the absolute worst thing was after the purchase was completed, it told me that the tickets wont be emailed to me until 4 days prior to the train trip. Now in the case of those particular tickets, that's going to be ok for me because I'll still be home 4 days prior to the train trip (I fly to Paris from San Francisco the next day), so if they show up on time I should have time to print them out before I leave.
But how is the traveler to deal with this when they buy tickets for later in their trips? Chase around what ever French town they happen to be in on that 4th day prior for a print shop and somehow get the emailed PDF ticket off their cell phone and into a printer? And who wants to deal with this while on vacation anyway? I'm trying to do everything in advance from home so I can relax and enjoy myself during the trip.
I called the SNCF help line. Nice lady who spoke English well, but no way to get those tickets emailed to me sooner.
In contrast, the www.trainline.eu site doesn't require any French cell numbers, took my VISA card without even a phone call to the issuing credit union and I got the ticket PDF files immediately. They emailed them to me immediately and the PDF files are presented as links to download at the bottom of the purchase receipt page, so I didn't even need to get the email. I've used the www.trainline.eu for all train ticket purchases subsequent to that first one from the SNCF site and all have gone without a hitch.
I've compared the prices presented on www.trainline.eu vs. those on the SNCF site and in all cases, the lowest www.trainline.eu site prices have been a bit less than those on the SNCF site. This was not the case on ricksteves.mytraintravel.com, where the lowest ticket prices were significantly higher than either of the other two (like 3 times as much).
In all fairness, the only reason I know about www.trainline.eu is because it was suggested to me by your excellent staff in response to an emailed query I made to you, so hats off to them for that one.
But you really should update the advice in your book (p. 1103 of Rick Steves France 2018) and on this site. I note that:
still recommends the usage of the SNCF site for advance ticket purchases.